Effects of Shark Removal on Spatial Partitioning Among Large Mesopredators on Coral Reefs

Effects of Shark Removal on Spatial Partitioning Among Large Mesopredators on Coral Reefs | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effects of Shark Removal on Spatial Partitioning Among Large Mesopredators on Coral Reefs Laura-Marie Dehne, Luciana C. Ferreira, Conrad Speed, Robert Harcourt, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8209051/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Coral reefs host high densities of large mesopredators occupying upper trophic levels. Understanding how these species partition space is essential to reveal underlying ecological dynamics and inform conservation. We hypothesised that red bass ( Lutjanus bohar ) and grey reef sharks ( Carcharhinus amblyrhynchos ) exhibit spatial and/or temporal partitioning influenced by species-specific behaviour and historical fishing pressure. To test this, we used acoustic telemetry to investigate habitat partitioning between these two large mesopredators at the Rowley Shoals and the Scott Reefs, Western Australia. These analyses were based on acoustic detections collected between 2007 and 2016 at the Rowley Shoals (17°20’S, 119°10’E) and the Scott Reefs (14°3’S, 121°46’E) on the north-western Australian continental shelf. Analysis of 95% kernel utilisation distributions (KUDs) showed broad spatial overlap, with both species frequently occupying habitats near reef fronts and channels. However, 50% KUDs revealed finer-scale partitioning: at the Rowley Shoals, core space use overlapped by less than 20%, whereas at the Scott Reefs, overlap exceeded 60%. These differences likely reflect historical fishing pressure, particularly the depletion of adult reef sharks at the Scott Reefs. There was little evidence of temporal partitioning. Both species were most active in the evening and highly resident in the same habitats throughout the year. Red bass exhibited wider-ranging movements from March to June, likely associated with spawning activity while grey reef sharks exhibited consistent presence and high site fidelity year-round. These findings underscore the influence of mesopredator size structure and abundance on spatial behaviour and highlight the conservation value of no-take marine reserves. acoustic telemetry coral reef competition fishing pressure Indo-Pacific KUD shark ecology spatial partitioning Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. INTRODUCTION The coexistence of ecologically similar species is often mediated through niche partitioning, a process grounded in the ecological principle that two species competing for the same resources cannot coexist indefinitely (Gause, 1932 ; Armstrong, 1976 ; Volterra, 1927). Such partitioning may occur across spatial, temporal, or trophic dimensions, thereby facilitating the cohabitation of functionally similar species (Ross, 1986 ; Truchy et al. 2019 ). This mechanism implies that each species plays a distinct role within the ecosystem, challenging the notion of functional redundancy. Indeed, evidence from coral reef ecosystems suggests that redundancy among coexisting species is often limited (D’Agata et al. 2016 ; Guillemot et al. 2011 ; Mouillot et al. 2014 ), underscoring the ecological significance of interspecific interactions in maintaining niche structure and community dynamics (Bascompte et al. 2005 ; Heithaus et al. 2008 ; Paine, 1992 ). Coral reef food webs are among the most structurally complex in marine systems, with high densities of apex and mesopredators (Lucifora et al. 2011 ; Pimiento et al. 2023 ). Despite the prevalence of predators, the mechanisms underlying their coexistence, particularly through spatial or temporal niche partitioning, remains poorly understood (van Zinnicq Bergmann et al. 2024 ). This knowledge gap is concerning, given that many large reef predators are heavily targeted by fisheries, contributing to their decline. Fishing pressure disproportionately affects large-bodied species, and global studies indicate that reef sharks, once the dominant mesopredators in these systems, are now functionally extinct on one-fifth of the world’s coral reefs (MacNeil et al. 2020 ). Their loss can disrupt trophic dynamics and reshape interactions among lower-order predators (Barley et al. 2017a , 2017b , Meekan et al. 2025 , Sherman et al. 2023 ). Two prominent mesopredators found across Indo-Pacific coral reefs are grey reef sharks ( Carcharhinus amblyrhynchos ) and red bass ( Lutjanus bohar ). Both are large-bodied, nocturnally active predators that share similar dietary preferences, including fish, cephalopods, and benthic invertebrates (Chin et al. 2012 ; Frisch et al. 2016 ; Barley et al. 2017a ). Grey reef sharks can attain up to 1.8 meters in length (Chin et al. 2012 ) and are typically associated with outer reef slopes and channels (Rizzari et al. 2014 ). Red bass, although smaller (typically 60 cm), are a large reef-dwelling teleost predator and frequently occupy similar habitats to grey reef sharks but display more restricted movements (Ferreira et al. 2025 ). The apparent overlap in their ecological niches raises questions about the mechanisms facilitating their coexistence in nutrient-limited coral reef environments (Grigg et al. 1984 ). Although these species co-occur, finer-scale partitioning, either temporally or spatially, may be needed to reduce direct competition. Acoustic telemetry, which uses arrays of submerged receivers to track tagged animals, is a powerful tool for studying such patterns of spatial ecology (Hussey et al. 2015 ; Mourier et al. 2016 ; van Zinnicq Bergmann et al. 2024 ). This technology allows researchers to investigate spatial and temporal patterns of movement simultaneously across multiple species (Speed et al. 2011 ; Williams et al. 2022). For example, acoustic telemetry combined with network analysis have shown that the movement patterns of grey reef sharks support much greater connectivity within a coral reef system than red bass movement, which generate strong, but localised connectivity (Ferreira et al 2025 ). A unique natural experiment off the northwest coast of Western Australia offers insight into how local-scale pressures might influence niche dynamics. Here, the Rowley Shoals, designated as a no-take marine protected area for over three decades, supports intact populations of reef sharks and mesopredatory teleosts (Speed et al. 2019 ). In contrast, a neighbouring reef system in the region called the Scott Reefs are subject to artisanal shark fishing by Indonesian fishers using longlines, an activity permitted under traditional access rights (Ruppert et al. 2013 ). The differential fishing pressure across these reef systems provides an opportunity to examine whether reduced shark populations alter spatial dynamics and interactions among co-occurring mesopredators. Previous studies in these systems have shown that declines in shark abundance correspond with shifts in mesopredator diet, condition, and community structure (Barley et al. 2017a , b ). Here, we test whether grey reef sharks and red bass exhibit spatial and/or temporal partitioning on coral reefs, and whether such partitioning is influenced by the relative abundance and size structure of these predators. We hypothesise that any spatial or temporal partitioning will be more pronounced in the more protected system of the Rowley Shoals, where larger reef sharks potentially outcompete or predate on red bass. In the fished system of the Scott Reefs, we expect more spatial and temporal overlap due to the absence or reduced abundance of larger reef sharks. Understanding these dynamics can help inform conservation strategies and improve our comprehension of predator interactions in coral reef ecosystems and provide insight into how the loss of these predators may affect overall ecosystem function. 2. METHODS 2.1. Study site The Rowley Shoals and the Scott Reefs are located at the north-western continental shelf off Australia, approximately 400 km from the coast (Fig. S1 ). These reef systems form part of the shelf-edge atoll complex on Australia’s north-west continental margin, rising steeply from deep water and exhibiting similar geomorphological and oceanographic conditions (Wilson 2013 ), providing a broadly comparable habitat template for fish and shark assemblages. Since 1990, the Rowley Shoals have been protected under various management regimes, with the lagoons of Imperieuse and Clerke Reef designated as no-take zones where all fishing is prohibited by the Western Australian Government (Department of Environment and Conservation 2006) and thus can be considered a somewhat “pristine” coral reef environment. In contrast, the Scott Reefs have a longstanding history of fishing activities, notably shark fishing by artisanal Indonesian fishers, a practice permitted by Australia in acknowledgement of traditional access to the reef that dates back many centuries (Environment Australia & Natural Heritage Trust, 2002; Edgar et al. 2020 ). 2.2. Acoustic tracking data The study used an existing acoustic telemetry dataset, freely available from the Integrated Marine Observing System-Animal Tracking Facility, accessible through the AODN portal ( https://portal.aodn.org.au/ ) (Hoenner et al. 2018 ). This dataset included acoustic tracking data for 63 grey reef sharks ( Carcharhinus amblyrhynchos ) and 25 red bass ( Lutjanus bohar ) detected by acoustic receiver arrays in the Rowley Shoals and the Scott Reefs. Red bass were tagged at both reef systems in 2015, whereas grey reef sharks were tagged over multiple years (2007, 2011, 2012 at the Rowley Shoals, and in 2011 at the Scott Reefs), with some temporal overlap between datasets (Figure S3, Table S1 ). The animals were equipped with InnovaSea V16 transmitters (for sharks) and V13 transmitters (for smaller sharks and red bass), with their movements monitored by arrays of passive acoustic receivers anchored to the seabed (Figure S1 b, c). These receivers are designed to log data when tagged animals enter their listening radius, which is typically around 300–500 m (Heupel et al. 2006 ). Tagging occurred at various shallow sites (Figure S1 d, e) strategically located near the reef crest and within the reef lagoons (Field et al. 2011 ) (Table S1 ). For details of the tagging techniques for grey reef sharks, see Field et al. ( 2011 ). Briefly, grey reef sharks were caught by hook and line, brought to the surface, and secured dorsal surface down against a boat to induce tonic immobility (Field et al. 2011 ). The sharks were sexed, measured and a small incision made for insertion of an acoustic tag in the abdominal cavity. The incision was then sutured closed, and the shark was released. This process generally took less than 15 minutes. Similarly, red bass were also tagged after capture by hook and line. Fish were landed on the vessel and held in a tank containing the anaesthetic Aqui-S. Once unconscious, the fish were held in a cradle and a tag inserted via a small incision in the abdomen. The cut was sutured closed, and the fish returned to a tank for recovery. After around 2 hours the fish were released. 2.3. Data analysis The acoustic telemetry dataset was analysed using RStudio Version 2023.03.1 + 446 and QGIS Version 3.26.3 – Buenos Aires. For the Rowley Shoals, which consists of three atolls separated by 28–44 km, the analysis specifically focused on Clerke Reef, the middle atoll (Figure S1 ), as red bass were exclusively tagged at this location and did not move among atolls. At Scott Reefs, the analysis encompassed both North and South Scott reefs due to their proximity to each other (~ 6 km), facilitating movement between the adjacent reefs. The receiver array at the Rowley Shoals and the Scott Reefs varied in size and number, requiring us to normalise detections by the number of receivers at each location. 2.4. Movement metrics Movement and habitat use metrics were calculated for each species at each reef system separately to allow comparisons between species and within and between reef systems. The number of detections received from tagged animals for each species and each reef system was used to identify preferred areas (90% of detection data). Abacus plots were created to visually inspect detection frequencies over time for each tagged individual during the operational lifespan of the tags (Kraft et al. 2023 ). A residency index (RI), ranging from 0 (never detected) to 1 (detected every possible day), was calculated for each individual as the ratio of days each animal was detected divided by total days the animal was detected within the acoustic array (e.g., date of last detection – date of first detection), offering insights into side fidelity and movement patterns (Appert et al. 2023 ). Centre of Activity (COA) (Simpfendorfer et al. 2002 ) for each species at each reef system was estimated based on weighted means of the number of concurrent detections across receivers with overlapping ranges during a given time period. We chose a 60-minute time period using the “COA” function from the “Vtrack” package (Udyawer et al. 2018 ) for each tagged animal with a minimum of five locations to allow for subsequent habitat use analysis. From these COA, Minimum Convex Polygons (MCP) were calculated using the “adehabitatHR” package (Calenge, 2023 ) in the software RStudio Version 2023.03.1 + 446, which delineates the smallest area encompassing all locations representing the minimal areas used by each individual. Kernel Utilisation Distributions (KUDs) were also calculated using the “adehabitatHR” package. The “kernelUD” function fits a bivariate probability density function to the location data (here we used the location of the COA), using the kernel smoothing parameter “href” (Kie, 2013 ), which we selected to ensure contiguous rather than disjoint utilisation distributions. However, because “href” is very sensitive to sample size, it may have resulted in inflated utilisation distributions, particularly during periods of low detection. To minimise potential biases from these inflated KUD metrics, we focused our overlap analyses on percentage-based comparisons rather than absolute area values. Range testing was not conducted when the receivers were deployed, therefore we used a conservative detection range of 300 m (Kessel et al. 2014 ). The areas of the 50% and 95% kernel utilisation distributions (KUD) were calculated for each individual but also for each species using all the locations for all individuals of a species in each reef system. Temporal patterns in space use were analysed by segmenting data into monthly, diurnal and nocturnal periods, and further into hourly intervals. Shapefiles from 50% and 95% KUDs were overlaid in QGIS and the overlap in area (km 2 ) between the utilisation distributions of red bass and grey reef sharks at both reef systems calculated in R. This analysis was done for each species combined at each reef system and for diurnal and nocturnal periods. In our spatial analysis of red bass we encountered significant challenges due to scattered detection patterns and sparse data, particularly during non-peak hours. This sparsity of data precluded the use of Brownian bridges for estimating movement paths (Horne et al. 2007 ) and limited the calculations of MCPs and KUDs. 3. RESULTS 3.1. Size and detections at receivers Tagged red basshad an average total length of 58.7 cm ± 4.8 at the Rowley Shoals and 48.8 cm ± 16.0 at the Scott Reefs (Table S1 ). Tagged grey reef sharks had a mean total length of 146.1 cm ± 19.5 at the Rowley Shoals and 131.1 cm ± 30.7 at the Scott Reefs. Both red bass and grey reef sharks tended to be larger at the Rowley Shoals than Scott Reefs (Fig. 1 , Kolmogorov-Smirnov test p < 0.0001). Tagged animals were detected on 27 of the 41 receivers deployed at the Rowley Shoals and on all 18 receivers deployed at the Scott Reefs (Table S1 ). Red bass were detected 43,627 times at the Rowley Shoals and 1,863 times at the Scott Reefs. At the Rowley Shoals, 90% of red bass detections were recorded by just four receivers, with detections spanning a total of 22 receivers (Figure S2a, Table S1 ). At the Scott Reefs, 90% of detections occurred on three receivers, with detections recorded across eight receivers in total (Figure S2b, Table S1 ). Grey reef sharks had a higher number of detections than red bass, with 409,626 detections dispersed across 27 receivers at the Rowley Shoals (Clerke Reef only), of which 90% were recorded by 15 receivers (Figure S2c, Table S1 ). At the Scott Reefs, grey reef sharks were detected 241,233 times across all 18 receivers, with 90% of detections concentrated on three receivers (Figure S2d, Table S1 ). Mean detections per receiver were 1,983 ± 3,656 and 233 ± 449 for red bass, and 15,117 ± 12,546 and 13,402 ± 34,044 for grey reef sharks at the Rowley Shoals and Scott Reefs, respectively (Table S1 ). Two of the three receivers most frequented by red bass were also those that recorded the most detections of tagged sharks at the Scott Reefs (Figure S2b, d). In contrast, at the Rowley Shoals, the five receivers that detected tagged red bass most frequently were not among those most used by sharks (Figure S2a, c). 3.2. Monthly detections Red bass detections were highest from April (tagging) to August at both locations, followed by a sharp decline in September (Fig. 2 a, b). At Rowley Shoals, detections dropped from > 6,000 during the first month to > 5,000 per month until August, whereas at the Scott Reefs, they declined from > 500 to 200–400 for the subsequent months until a sharp decline in September (< 100). For grey reef sharks, the frequency of detections was more consistent throughout the year at both reef systems (Fig. 2 c, d). The highest number of detections occurred in October (tagging occurred in September and December) at the Rowley Shoals (Fig. 2 c), and more detections were recorded in December (tagging) and January at the Scott Reefs (Fig. 2 d). 3.3. Hourly detections At both the Rowley Shoals and the Scott Reefs, the number of detections of red bass increased throughout the day and into the evening, after a low in early morning hours (Fig. 3 a, b). Patterns in detections at the Scott Reefs were more variable on an hour-to-hour basis than at the Rowley Shoals (Fig. 3 b). For grey reef sharks, the detection frequency was more consistent throughout the day in both reef systems (Fig. 3 c, d), although the highest number of detections occurred from 20–22.00 hrs (> 20,000 detections) at the Rowley Shoals (Fig. 3 c), and peaked both around midday and at 22.00 hrs (~ 12,000 detections) at the Scott Reefs (Fig. 3 d). 3.4. Site fidelity There was high variability in detection frequencies among individual red bass and grey reef sharks at both the Rowley Shoals and the Scott Reefs (Figure S3). At the Rowley Shoals, the data for red bass spanned from May 2015 to September 2016, with three individuals resident within the array, three individuals ceasing transmission after a few weeks and most others recording very regularly dispersed detections, that included simultaneous gaps in the data during June and July of both years (Figure S3a). Red bass were tracked at the Scott Reefs from April 2015 to September 2016 (Figure S3b). Although detection frequencies also varied among individual red bass, there were less synchronous patterns among individuals (Figure S3a, b) at Scott Reefs than at the Rowley Shoals. Grey reef sharks were tagged in December 2007 and September 2011 at the Rowley Shoals. After the first deployment of tags, sharks were detected from December 2007 to November 2008 (Figure S3c) and in the second deployment they were detected from September 2011 to February 2016 in (Figure S3d). In both of these periods, patterns of residency were very similar, with most tagged sharks ( n = 31) exhibiting nearly constant patterns of detection over long periods (Figure S3c, d), with only four sharks ceasing transmission after two to four months (Figure S3c, d). At the Scott Reefs, grey reef sharks were tagged in December 2011 and were detected by the receiver array until May 2016 when the receiver array was removed (Figure S3e). Only one shark ceased transmission after more than six months. Sharks displayed detection patterns that ranged from resident to intermittent (Figure S3e). 3.5. Residency At the Rowley Shoals, individual red bass exhibited variable patterns of residency indices ranging from very high (residency index > 0.75) to very low (residency index 0.75 and four red bass displaying almost no residency in the array (residency index 0.5 (Fig. 4 c), and 10 with very high residency (residency index > 0.75). Similarly, at the Scott Reefs, grey reef sharks also had higher residency indices overall (6 individuals with residency index > 0.5) (Fig. 4 d) than red bass. Statistical analysis further supports these observations, and the Wilcoxon Rank Sum Test revealed a significant difference in the residency indices between red bass and grey reef sharks (p = 0.0088), suggesting that grey reef sharks exhibited stronger or more consistent residency patterns at both locations. Bootstrap confidence intervals for the mean residency indices (95% CI for red bass: 0.1992 to 0.4535; grey reef sharks: 0.4352 to 0.5905) further indicated that on average, grey reef sharks had higher residency indices than red bass. 3.6. Spatial distribution Minimum Convex Polygon (MCP) for all detections of red bass at the Rowley Shoals covered an area of 13.95 km², delimited by 26 receivers (Fig. 5 a, Tables S1, S2). This area included receivers both inside and outside the lagoon at Clerke Reef. The most distant receivers were located on the fore reef, one approximately 4 km north of the channel and another near the reef crest about 9.4 km to the south (Fig. 5 a). The MCP for all detections of red bass at the Scott Reefs covered an area of 8.84 km², delimited by 8 receivers (Fig. 5 b, Tables S1, S2). The MCP only encompassed receivers at North Scott but included areas both inside and outside the lagoon. The furthest receiver was located on the fore reef, 6 km south of the channel on the reef crest (Fig. 5 b). The 95% Kernel Utilisation Distribution (KUD) for all detections of red bass at the Rowley Shoals identified three areas. A large area stretched from inside the lagoon along the channel and around the reef crest, with two smaller areas positioned north of the channel along the reef crest (Fig. 5 a). Together these encompassed an area of 3 km 2 (Table S2). In contrast, the 95% KUD for red bass at the Scott Reefs included two extended areas. The first, smaller area was located inside the lagoon, whereas the second extended outside the channel along the reef crest (Fig. 5 b). Together, these encompassed an area of 2.77 km 2 (Table S2). At the Rowley Shoals, the 50% KUD for all detections of red bass included three small core areas, two of which were located inside the lagoon, and a third, more elongated area, extended outside the channel along the reef crest (Fig. 5 b). These encompassed an area of 0.38 km² (Table S2), smaller than the corresponding area at the Scott Reefs (Table S2). The 50% KUD for red bass at the Scott Reefs included one small core area, located just outside the channel (Fig. 5 b), encompassing an area of 0.44 km² (Table S2), which was slightly larger than the area of the KUD of the species at the Rowley Shoals. Grey reef sharks exhibited larger areas of MCPs and KUDs than red bass (Fig. 5 c, d, Table S2). The MCP for grey reef sharks at the Rowley Shoals covered an area of 14.57 km 2 , delimited by 27 receivers (Table S2). This included areas inside and outside the lagoon, with the most distant receivers located in the fore reef around 4 km north of the channel around the reef crest and about 9.4 km south of the channel (Fig. 5 c). At the Scott Reefs, the MCP for all detections of grey reef sharks spanned a large area of 214.94 km 2, delimited by 18 receivers (Fig. 5 d, Tables S1, S2). This MCP included receivers positioned inside and outside the lagoon, north of the channel, as well as in the south of North Scott and South Scott Reef, with the furthest receiver located in the fore reef about 6 km north of the channel around the reef crest and approximately 18 km south of the channel, near the edge of South Scott (Fig. 5 d). The 95% KUD for grey reef sharks at the Rowley Shoals had four extended areas, the largest spanning from inside the lagoon, along the channel, and around the reef crest, and three smaller areas, two located north of the channel and one south of the channel along the reef crest (Fig. 5 c). These totalled an area of 4.89 km 2 (Table S2). At the Scott Reefs, the 95% KUD for grey reef sharks was smaller than at the Rowley Shoals, with a single area located just outside the channel (Fig. 5 d), encompassing 3.15 km 2 (Table S2). The 50% KUD for grey reef sharks at the Rowley Shoals consisted of four smaller core areas, one located inside the lagoon, another elongated area directly in front of the channel and two further north along the reef crest (Fig. 5 c), with a total area of 1.25 km 2 (Table S2). The 50% Kernel Utilisation Distribution (KUD) at this reef system had one core area, located just in front of the channel (Fig. 5 d) and encompassing an area of 0.64 km 2 (Table S2). Overall, the 50% Kernel utilisation distributions for both species at both reef systems occurred near the channel, inside the lagoon and outside the fore reef. 3.7. Monthly spatial distribution For red bass, the monthly analysis of residency was limited to MCPs due to the low number of detections in some months (Figures S4, S5), variations in number of detected individuals in some months (Figure S5, Table S3, S4), individual variability (Table S7), and large gaps in the data (Figure S3). This prevented the calculation of monthly KUDs for the species. The MCP analysis revealed that red bass occupied a larger area between March and May at both reef systems (Figure S5a, S5b), with a marked reduction in space use during the remainder of the year. In contrast, grey reef sharks were detected by a relatively consistent number of receivers throughout the year (Figure S4, S5, Table S5, S6), allowing for the calculation of both MCP and KUD metrics on a monthly basis. The spatial metrics for grey reef sharks at the Rowley Shoals indicated consistent space use year-round, although a noticeable decrease in area of the MCP occurred between November and January. This reduction in area did not occur in the 95% and 50% KUDs (Figure S5c). At the Scott Reefs, although the MCP areas showed large fluctuations over the year, the areas for the 95% and 50% KUDs remained relatively constant (Figure S5d). 3.8. Diel spatial distribution During the day, the 95% KUD for red bass at the Rowley Shoals encompassed three extended areas: one large area that spanned from inside the lagoon along the channel and around the reef crest, and two smaller areas located north of the channel along the reef crest (Figure S6a). These covered an area of 3.73 km 2 (Table S2). At night, the 95% KUD still identified three extended areas, but with slightly different configurations: a large area from inside the lagoon along the channel and extending to the outer channel at the reef crest, and two smaller areas, one north of the channel at the reef crest and another smaller area inside the lagoon (Figure S6b). These totalled an area of 2.72 km 2 (Table S2). At the Scott Reefs, the 95% KUD of red bass during the daytime had two extended areas: a smaller area inside the lagoon and another outside the channel along the reef crest (Figure S6c) that encompassed an area of 3.64 km 2 (Table S2). At night, the KUD was similar but slightly reduced, featuring two extended areas that closely resembled daytime patterns with one inside the lagoon and the other just outside the channel along the reef crest (Figure S6d). These covered an area of 3.01 km 2 (Table S2). During the day, the 50% KUD for red bass at the Rowley Shoals identified two core areas: one just outside the channel and another inside the lagoon south of the channel (Figure S6a), which together covered an area of 0.44 km² (Table S2). At night, the 50% KUD at the Rowley Shoals revealed a more fragmented pattern, with four smaller core areas: two inside the lagoon and outside the channel, one directly in front of the channel, and another slightly further south along the reef crest (Figure S6b), totalling an area of 0.36 km² (Table S2). At the Scott Reefs, the daytime 50% KUD for red bass identified one core area located just outside the channel (Figure S6c), encompassing an area of 0.59 km² (Table S2). Similarly, the night-time 50% KUD also identified a core area just outside the channel (Figure S6d), which was slightly smaller than during the day, measuring 0.50 km² (Table S2). Both daytime and night-time core areas at the Scott Reefs were very similar in location and shape. The 95% KUD for all detections of grey reef sharks at the Rowley Shoals revealed almost identical space use during day and night. Four distinct areas were identified: a large area extending from inside the lagoon along the channel and around the reef crest, two smaller areas positioned north of the channel along the reef crest, and one area to the south of the channel (Figure S6e, f). These covered an area of 5.44 km 2 (Table S2). At night, the overall area of the KUD remained similar, totalling 5.48 km 2 (Table S2). The 95% KUD of grey reef sharks was less extensive at the Scott Reefs than the Rowley Shoals. During the day, it comprised an extended area outside the channel along the reef crest (Figure S6g) and covered an area of 4.53 km 2 (Table S2). At night, the 95% KUD occurred in a similar location (Figure S6h) but decreased in size to 2.97 km 2 (Table S2). During the day the 50% KUD of grey reef sharks at the Rowley Shoals identified two core areas of use: one larger area stretching from inside the lagoon, through the channel, and north along the reef crest, and another located further north of the channel (Figure S6e), encompassing an area of 1.4 km² (Table S2). At night, the 50% KUD formed a less continuous pattern, with four core areas: two larger areas positioned inside the lagoon and just in front of the channel, and two additional areas further north of the channel (Figure S6f). Total area of the KUD was similar to the daytime at around 1.4 km 2 (Table S2). At the Scott Reefs, the daytime 50% KUD of grey reef sharks covered one core area, situated just outside the channel and slightly elongated to the south (Figure S6g), with a total area of 0.84 km 2 (Table S2). This pattern persisted at night (Figure S6h), albeit with a slight reduction in size, resulting in a core area measuring 0.59 km 2 (Table S2). 3.9. Overlap of space use At the Rowley Shoals, the 50% KUD of red bass overlapped by 18.6% with the 50% KUD of grey reef sharks (Table 1 ). The core use areas (50% KUD) of red bass (purple; Fig. 6 a) were largely separate from the core use areas of grey reef sharks (rose; Fig. 6 a). In the lagoon, much of the red bass core use area did not overlap with the core use area of sharks. Outside the lagoon, sharks primarily used the northern outer reef crest while red bass concentrated around the channel and slightly south of it (Fig. 6 a). When considering 95% KUDs of red bass and grey reef sharks, overlap increased to 71.48% (Table 1 ). Both red bass and grey reef sharks used extensive areas around the lagoon and along the reef crest, extending northwards from the channel (Fig. 6 b). Table 1 Spatial overlap of areas of 50% and 95% Kernel Utilization Distributions (KUD) of red bass and grey reef sharks at the Rowley Shoals and the Scott Reefs, for pooled data sets and split by day and night. The table shows the reef system, time of day (ToD), and KUD type, overlap of areas of 50% and 95% KUD of red bass with grey reef shark in km 2 . Reef System ToD KUD Type Overlap area (km 2 ) Overlap red bass (%) Rowley Shoals Combined 50% 0.07 18.60 Rowley Shoals Day 50% 0.10 17.97 Rowley Shoals Night 50% 0.07 20.38 Rowley Shoals Combined 95% 2.14 71.48 Rowley Shoals Day 95% 2.62 70.28 Rowley Shoals Night 95% 2.00 73.62 Scott Reefs Combined 50% 0.28 64.28 Scott Reefs Day 50% 0.40 68.52 Scott Reefs Night 50% 0.29 57.99 Scott Reefs Combined 95% 1.46 52.87 Scott Reefs Day 95% 1.86 51.13 Scott Reefs Night 95% 1.61 53.65 At the Scott Reefs, red bass and grey reef sharks had a higher overlap of 50% KUDs (64.28%; Table 1 ) than at the Rowley Shoals, with both species sharing the same core area just in front of the channel outside the lagoon (Fig. 6 c). The 95% KUDs of red bass and grey reef sharks overlapped by 52.87% (Table 1 ). This lower overlap was largely due to red bass extending their use area inside the lagoon, whereas grey reef sharks extended their use area outside the channel along the outer reef crest (Fig. 6 d). 3.10. Diel overlap of space use At the Rowley Shoals, the overlap of core areas (50% KUDs) between red bass and grey reef sharks was low, ranging between 17.97% during the day and 20.38% at night (Table 1 ). In contrast, the overlap of broader areas (95% KUDs) was consistently high, with 70.28% during the day and 73.63% during the night (Table 1 ). At the Scott Reefs, core overlap was much higher, with 50% KUDs overlapping by 68.52% during the day and 57.99% at night. Overlap of 95% KUDs at Scott was lower overall, with 51.13% during the day and 53.65% during the night (Table 1 ). 4. DISCUSSION We used acoustic telemetry to investigate spatial and temporal partitioning between red bass ( Lutjanus bohar ) and grey reef sharks ( Carcharhinus amblyrhynchos ) within two coral reef ecosystems in northwest Australia. Given the ecological similarities and overlapping habitats of these species, we hypothesised that they might partition space at fine temporal (hours-days) and/or spatial (hundreds of meters to kilometres) scales to facilitate coexistence. Although we found little evidence for temporal partitioning, as both species were active at similar times during the diel cycles and had high residency indices, our results provided partial support for spatial partitioning. Both species were associated with key geomorphological features in both reef systems—reef channels, outer reef crest, and lagoonal areas adjacent to channel mouths—resulting in high overlap of 95% kernel utilisation distributions (KUDs). However, analyses of core activity spaces (50% KUDs) revealed differences in fine-scale spatial use between the species. At the Rowley Shoals, only a small part (18.6%) of the 50% KUD of red bass overlapped that of grey reef sharks, indicating that the areas of most intensive use by each species were largely distinct. In contrast, at the Scott Reefs, 64.3% of the red bass 50% KUD overlapped with that of grey reef sharks. These contrasting patterns might be explained by differences in shark abundance and size structure between reef systems. Grey reef sharks are almost three times more abundant at the unfished Rowley Shoals than at the Scott Reefs, where populations have been depleted by targeted fishing (Lester et al. 2021 ). Moreover, surveys using baited remote underwater video systems show that at the Scott Reefs, populations of grey reef sharks are mostly composed of smaller juveniles, whereas at the Rowley Shoals, there are higher numbers of large, adult sharks (Figure S7). This disparity in size between the two species may contribute to spatial segregation at Rowley Shoals, where large adult sharks may pose a threat to red bass either through predation or interference competition. In contrast, at the Scott Reefs, smaller juvenile sharks are less likely to exclude red bass from shared habitats, resulting in greater overlap of core space use. These patterns are consistent with previous studies showing that mesopredators and prey often avoid areas where dominant predators are abundant (Arias-Del Razo et al. 2012 , Heithaus 2005 , Heithaus et al. 2007 , 2008 , Johnson et al. 2007 , Wirsing et al. 2007a , b ). Grey reef sharks and red bass had centres of activity around and within the reef channel and on the outer reef crest. Both species probably take advantage of the opportunity for energy saving offered by the currents, eddies and updrafts that the restriction and resulting acceleration of water flow creates as it passes through the channel. It has been estimated that updrafts induced by the current in channel systems and on reef slopes in French Polynesia can reduce energy expenditures of grey reef sharks by 10–15%, (Papastamatiou et al. 2021 ). Similar energy savings are likely to be available to other reef fishes such as red bass and may be one reason that channels and reef passes are habitats where many species of large reef fishes congregate during the day (Fisher et al. 2018 ). Additionally, reef passages may also aggregate both plankton and the small planktivorous fishes that are likely to be the prey of these mesopredators, particularly on incoming tides (Fisher et al. 2018 , Papastamatiou et al. 2025 ). Because of the opportunity for energy conservation and food acquisition, outer reef crest and channel entrance habitats are likely to be occupied by the largest, competitively dominant reef sharks (Papastamatiou et al. 2021 ). Where these large individuals have been removed by fishing, as is the case at Scott Reefs, it may offer the opportunity for smaller, juvenile sharks to reside in these habitats. These smaller sharks would otherwise be competitively excluded or subject to predation by larger adults. This may explain why, at the Rowley Shoals, grey reef sharks occupied habitats across the lagoon and outer reef slope whereas at the Scott Reefs, where the largest adult sharks have been removed by fishing, the remaining juvenile grey reef sharks we tagged occurred on outer reef slopes and in the channel and were rarely detected in the lagoon. This absence of grey reef sharks from habitats occupied by red bass at Scott Reefs may also account for the shift in diet of this teleost mesopredator between these reef systems. Barley et al. (2017 a) found that on the Scott Reefs, the diet of red bass included a much greater proportion of pelagic prey such as fishes and squid than at the Rowley Shoals, where the diet had a much larger component of benthic invertebrates. Such differences in diet have the potential to create trophic cascades in coral reef ecosystems (Meekan et al. 2025 ). Both red bass and grey reef sharks were more active in the evenings in both reef systems. Detections of grey reef sharks by receivers were similar throughout most times of the day and peaked in the early evening, whereas detections of red bass climbed steadily from the late afternoon to peak in the late evening in both reef systems. These patterns are consistent with the characterisation of these species as mostly nocturnal predators (Nagelkerken et al. 2000 ) and suggest that these species were not displaying temporal patterns of resource partitioning. The reef habitats used by grey reef sharks showed little change in both location and extent between night and day, although there was a small reduction in area of reef used by red bass at night. This reduction could reflect the greater activity of reef sharks at this time, and/or changes in the spatial distribution of prey. Although the Scott Reefs and Rowley Shoals offer a unique natural experiment to compare the impact of reef sharks on mesopredator communities, as others have noted, such uncontrolled comparisons are open to a variety of alternative scenarios that might explain our results (Barley & Meeuwig 2017 ). For example, differences in the spatial patterns of overlap between sharks and red bass might be due to changes in the distribution of some key resource (e.g. food, shelter) between these reef systems. We cannot exclude this possibility, although our results were consistent with a priori predictions of what might occur if competition between these large mesopredators was an important driver of distribution patterns. Additionally, previous analysis with the same tacking dataset used here showed grey reef sharks display greater movement extent within an atoll (Clerke Reef) and across a reef system (Rowley Shoals or Scott Reefs) than red bass, but connectivity patterns differed between male and female sharks (Ferreira et al 2025 ). Our sample size for red bass was also limited, which may have influenced the strength of some inferences made from our results. The configuration of acoustic arrays and occasional tag collisions may have further constrained the number of red bass that could be effectively monitored, as is common for species with small home ranges (Kessel et al. 2014 ). However, grey reef shark data from 2008 and 2015 deployments yielded consistent spatial patterns, suggesting robust characterisation of their movement and residency behaviour. Red bass exhibited more sporadic detections than sharks, perhaps due to their closer association with reef structure, which may interfere with tag transmissions. At the Rowley Shoals, there were regular monthly cycles in detections of red bass. Why these patterns occurred is not clear, but they may reflect cycles in the availability of prey in the water column or near the benthos, with ascent by the red bass to feed increasing the likelihood of tag transmissions being detected by the receiver stations, or alternatively, the presence of food within the reef matrix decreasing the likelihood of detection. Gaps in detections from March to June coincided with increased minimum convex polygon (MCP) areas, which may reflect seasonal spawning movements (Marriott et al. 2007 , Wright et al. 1986 ). At the Scott Reefs, there was little predictability in the sporadic pattern of transmissions of tagged red bass. Additional data are needed to better understand the mechanisms of spatial partitioning and trophic dynamics of red bass and grey reef sharks. Analyses of movement in relation to tidal and lunar cycles could improve understanding of habitat use, particularly in dynamic channel environments (Laurioux et al. 2024 ). The use of depth sensors and accelerometers would provide valuable insight into vertical movements, energetic expenditure, and habitat utilisation (Papastamatiou et al. 2021 , Vianna et al. 2013 ). Stable isotope analysis of tissues collected during tagging could complement telemetry data and clarify dietary overlap and resource partitioning (Tilley et al. 2013 ). Baited Remote Underwater Video (BRUV) systems could further elucidate behavioural interactions and risk effects between these mesopredators (Lester et al. 2020 , 2021 , 2022 ). Residency indices were high for many individuals of both species at both study locations supporting previous findings of strong site fidelity in reef-associated predators (Espinoza et al. 2015 ). The restricted spatial extent of core activity areas suggests that both species may be effectively managed through appropriately designed marine protected areas (MPAs). These findings reinforce the importance of integrating ecological knowledge into spatial conservation planning for reef-associated predators. 5. CONCLUSION Our study underscores the complex interactions between red bass and grey reef sharks at Scott Reefs and Rowley Shoals. On reefs with higher abundances of sharks, we observed some spatial partitioning in areas of core use by these species. This suggests that the presence of sharks influence the spatial behaviour of red bass, potentially as an adaptive strategy to reduce competitive pressures or predation risks. However, multiple mechanisms can support this coexistence. Given the variability in interactions we observed - from significant overlaps to possible spatial partitioning - it is clear that the organisation of space is not the only driving force allowing co-existence of these species. Other forms of resource partitioning, such as dietary differences (Barley et al. 2017a , b ), could support the coexistence of these mesopredators in the same habitats, for instance through plasticity in diet driven by differing predation pressure or environmental conditions between reefs. This complexity, and the possible influence of human threats such as fishing on shark abundance and spatial dynamics highlight the need for further research and targeted conservation efforts that are sensitive to the fine-scale interdependencies and unique roles large mesopredators have within coral reef ecosystems. Declarations Conflict of Interest The authors declare that they have no competing interests. Ethics Approval This research used existing acoustic telemetry data collected under animal ethics approvals reported in Field et al. ( 2011 ). No new animal handling occurred for this study. Funding This research was supported by the Australian Institute of Marine Science (AIMS) and the Integrated Marine Observing System (IMOS), and conducted as part of a Master’s research project within the International Master of Science in Marine Biological Resources (IMBRSea) programme. Authors’ Contribution All authors meet authorship criteria, have approved the submitted version, and agree to publication. The work is original and not under consideration elsewhere. Acknowledgement This study was supported by the Australian Institute of Marine Science and the Australian Integrated Marine Observing System (IMOS). Data were sourced from IMOS and is enabled by the National Collaborative Research Infrastructure Strategy (NCRIS). This work was part of the International Master of Science in Marine Biological Resources (IMBRSea) by LMD and was supported by the Oceans Institute at the University of Western Australia. Data Availability Acoustic tracking data from the Integrated Marine Observing System-Animal Tracking Facility is freely accessible through the AODN portal ( https://portal.aodn.org.au/ ). The R code used in this study will be available upon request References Appert C, Udyawer V, Simpfendorfer CA, Heupel MR, Scott M, Currey-Randall LM, Harborne AR, Jaine F, Chin A (2023) Use, misuse, and ambiguity of indices of residence in acoustic telemetry studies. Mar Ecol Prog Ser 714:27–44 Arias-Del Razo I, Hernández L, Laundré JW, Velasco-Vázquez L (2012) The landscape of fear: habitat use by a predator (Canis latrans) and its main prey ( Lepus californicus and Sylvilagus audubonii ). Can J Zool 90:683–693 Armstrong RA, McGehee R (1976) Coexistence of species competing for shared resources. Theor Popul Biol 9:317–328 Barley SC, Clark TD, Meeuwig JJ (2020) Ecological redundancy between coral reef sharks and predatory teleosts. Rev Fish Biol Fish 30:153–172 Barley SC, Meekan MG, Meeuwig JJ (2017a) Diet and condition of mesopredators on coral reefs in relation to shark abundance. PLoS ONE 12:e0165113 Barley SC, Meekan MG, Meeuwig JJ (2017b) Species diversity, abundance, biomass, size and trophic structure of fish on coral reefs in relation to shark abundance. Mar Ecol Prog Ser 565:163–179 Barley SC, Meeuwig JJ (2017) The power and pitfalls of large-scale. unreplicated Nat experiments Ecosystems 20:331–339 Bascompte J, Melián CJ, Sala E (2005) Interaction strength combinations and the overfishing of a marine food web. Proc Natl Acad Sci USA 102:5443–5447 Bradley D, Conklin E, Papastamatiou YP, McCauley DJ, Pollock K, Pollock A, Kendall BE, Gaines SD, Caselle JE (2017) Resetting predator baselines in coral reef ecosystems. Sci Rep 7:43131 Calenge C (2023) Home range estimation in R: the adehabitatHR package. R package documentation Chin A, Tobin A, Simpfendorfer C, Heupel M (2012) Reef sharks and inshore habitats: patterns of occurrence and implications for vulnerability. Mar Ecol Prog Ser 460:115–125 D’Agata S, Vigliola L, Graham NAJ, Wantiez L, Parravicini V, Villéger S, Mou-Tham G, Frolla P, Friedlander AM, Kulbicki M, Mouillot D (2016) Unexpected high vulnerability of functions in wilderness areas: evidence from coral reef fishes. Proc R Soc B 283:20160128 Edgar G, Mellin C, Turak E, Stuart-Smith R, Cooper A, Ceccarelli D (2020) Reef Life Survey assessment of coral reef biodiversity in the North-west Marine Parks Network. Reef Life Survey Foundation Inc., Hobart Environment Australia (2002) Ashmore Reef National Nature Reserve and Cartier Island Marine Reserve management plans. Environment Australia, Canberra Espinoza M, Heupel MR, Tobin AJ, Simpfendorfer CA (2015) Residency patterns and movements of grey reef sharks ( Carcharhinus amblyrhynchos ) in semi-isolated coral reef habitats. Mar Biol 162:343–358 Ferreira LC, Galaiduk R, Radford B, Udyawer V, Meekan M, Thums M, Harcourt R, Lee KA, Treml EA (2025) Marine predator movements create seascape connectivity in remote coral-reef ecosystems. Mov Ecol 13:72 Field IC, Meekan MG, Speed CW, White W, Bradshaw CJA (2011) Quantifying movement patterns for shark conservation at remote coral atolls in the Indian Ocean. Coral Reefs 30:61–71 Fisher EE, Choat JH, McCormick MI, Cappo M (2018) Relative influence of environmental factors on the timing and occurrence of multi-species coral reef fish aggregations. PLoS ONE 13:e0209234 Frisch AJ, Ireland M, Rizzari JR, Lönnstedt OM, Magnenat KA, Mirbach CE, Hobbs JPA (2016) Reassessing the trophic role of reef sharks as apex predators on coral reefs. Coral Reefs 35:459–472 Gause GF (1932) Experimental studies on the struggle for existence. J Exp Biol 9:389–402 Graham NAJ, Spalding MD, Sheppard CRC (2010) Reef shark declines in remote atolls highlight the need for multi-faceted conservation action. Aquat Conserv Mar Freshw Ecosyst 20:543–548 Grigg RW, Polovina JJ, Atkinson MJ (1984) Model of a coral reef ecosystem. Coral Reefs 3:23–27 Guillemot N, Kulbicki M, Chabanet P, Vigliola L (2011) Functional redundancy patterns reveal non-random assembly rules in a species-rich marine assemblage. PLoS ONE 6:e26735 Heithaus MR (2005) Habitat use and group size of pied cormorants ( Phalacrocorax varius ) in a seagrass ecosystem: possible effects of food abundance and predation risk. Mar Biol 147:27–35 Heithaus MR, Frid A, Wirsing AJ, Dill LM, Fourqurean JW, Burkholder D, Thomson J, Bejder L (2007) State-dependent risk-taking by green sea turtles mediates top-down effects of tiger shark intimidation in a marine ecosystem. J Anim Ecol 76:837–844 Heithaus MR, Frid A, Wirsing AJ, Worm B (2008) Predicting ecological consequences of marine top predator declines. Trends Ecol Evol 23:202–210 Heupel MR, Semmens JM, Hobday AJ (2006) Automated acoustic tracking of aquatic animals: scales, design and deployment of listening station arrays. Mar Freshw Res 57:113–122 Hoenner X, Huveneers C, Steckenreuter A, Simpfendorfer C, Tattersall K, Jaine F, Atkins N, Babcock R, Brodie S, Burgess J, Campbell H, Heupel M, Pasquer B, Proctor R, Taylor MD, Udyawer V, Harco R (2018) Australia’s continental-scale acoustic tracking database and its automated quality control process. Sci Data 5:180206 Horne JS, Garton EO, Krone SM, Lewis JS (2007) Analyzing animal movements using Brownian bridges. Ecology 88:2354–2363 Hussey NE, Kessel ST, Aarestrup K, Cooke SJ, Cowley PD, Fisk AT, Harcourt RG, Holland KN, Iverson SJ, Kocik JF, Mills Flemming JE, Whoriskey FG (2015) Aquatic animal telemetry: a panoramic window into the underwater world. Science 348:1255642 Johnson CN, Isaac JL, Fisher DO (2007) Rarity of a top predator triggers continent-wide collapse of mammal prey: dingoes and marsupials in Australia. Proc R Soc B 274:341–346 Kessel ST, Cooke SJ, Heupel MR, Hussey NE, Simpfendorfer CA, Vagle S, Fisk AT (2014) A review of detection-range testing in aquatic passive acoustic telemetry studies. Rev Fish Biol Fish 24:199–218 Kie JG (2013) A rule-based ad hoc method for selecting a bandwidth in kernel home-range analyses. Anim Biotelem 1:13 Kraft S, Gandra M, Lennox RJ, Mourier J, Winkler AC, Abecasis D (2023) Residency and space-use estimation methods based on passive acoustic telemetry data. Mov Ecol 11:2 Laurioux A, Huveneers C, Papastamatiou Y, Planes S, Ballesta L, Mourier J (2024) Abiotic drivers of the space use and activity of gray reef sharks Carcharhinus amblyrhynchos in a dynamic tidal environment. J Fish Biol 105:15–30 Lester EK, Langlois TJ, Simpson SD, McCormick MI, Meekan MG (2020) The hemisphere of fear: the presence of sharks influences the three-dimensional behaviour of large mesopredators in a coral reef ecosystem. Oikos 129:1371–1384 Lester EK, Langlois TJ, Simpson SD, McCormick MI, Meekan MG (2021) Reef-wide evidence that the presence of sharks modifies behaviours of teleost mesopredators. Ecosphere 12:e03301 Lester EK, Langlois T, Lindgren I, Birt M, Bond T, McLean D, Vaughan B, Holmes TH, Meekan MG (2022) Drivers of variation in occurrence, abundance and behaviour of sharks on coral reefs. Sci Rep 12:4024 Lucifora LO, García VB, Worm B (2011) Global diversity hotspots and conservation priorities for sharks. PLoS ONE 6:e19356 MacNeil MA, Chapman DD, Heupel M, Simpfendorfer CA, Heithaus M, Meekan M, Harvey E, Goetze J, Kiszka J, Bond ME, Currey-Randall LM, Speed CW, Sherman CS, Rees MJ, Udyawer V, Flowers KI, Clementi G, Valentin-Albanese J, Gorham T, Cinner JE (2020) Global status and conservation potential of reef sharks. Nature 583:801–806 Marriott RJ, Mapstone BD, Begg GA (2007) Age-specific demographic parameters and their implications for management of the red bass Lutjanus bohar (Forsskål 1775): a large, long-lived reef fish. Fish Res 83:204–215 Meekan MG, Lester EK, Kron FJ, Barneche DR (2025) Predator removals, trophic cascades and outbreaks of crown-of-thorns starfish on coral reefs. Commun Biol 8:305 Mitchell JD, Schifiliti M, Birt MJ, Bond T, McLean DL, Barnes PB, Langlois TJ (2020) A novel experimental approach to investigate the potential for behavioural change in sharks in the context of depredation. J Exp Mar Biol Ecol 530–531:151440 Mouillot D, Villéger S, Parravicini V, Kulbicki M, Arias-González JE, Bender M, Chabanet P, Floeter SR, Friedlander A, Vigliola L, Bellwood DR (2014) Functional over-redundancy and high functional vulnerability in global fish faunas on tropical reefs. Proc Natl Acad Sci USA 111:13757–13762 Mourier J, Maynard J, Parravicini V, Ballesta L, Clua E, Domeier ML, Planes S (2016) Extreme inverted trophic pyramid of reef sharks supported by spawning groupers. Curr Biol 26:2011–2016 Munroe S, Huveneers C (2019) Monitoring the presence and residency of sharks at key locations off Victor Harbor (Encounter Marine Park). Report 2. Flinders University, Adelaide. (March 2016 – October 2018 Nagelkerken I, Dorenbosch M, Verberk WCEP, Cocheret de la Morinière E, van der Velde G (2000) Day–night shifts of fishes between shallow-water biotopes of a Caribbean bay, with emphasis on the nocturnal feeding of Haemulidae and Lutjanidae. Mar Ecol Prog Ser 194:55–64 Paine RT (1992) Food-web analysis through field measurement of per capita interaction strength. Nature 355:73–75 Papastamatiou YP, Huveneers C, Ballesta L, Planes S, Mourier J (2025) Marine predator super-habitats: channels used for foraging, resting, mating, and parturition in sharks. Biol Conserv 311:111446 Papastamatiou YP, Iosilevskii G, Di Santo V, Huveneers C, Hattab T, Planes S, Ballesta L, Mourier J (2021) Sharks surf the slope: current updrafts reduce energy expenditure for aggregating marine predators. J Anim Ecol 90:2302–2314 Papastamatiou YP, Wetherbee BM, Lowe CG, Crow GL (2006) Distribution and diet of four species of carcharhinid shark in the Hawaiian Islands: evidence for resource partitioning and competitive exclusion. Mar Ecol Prog Ser 320:239–251 Pimiento C, Albouy C, Silvestro D, Mouton TL, Velez L, Mouillot D, Judah AB, Griffin JN, Leprieur F (2023) Functional diversity of sharks and rays is highly vulnerable and supported by unique species and locations worldwide. Nat Commun 14:7691 Rizzari JR, Frisch AJ, Connolly SR (2014) How robust are estimates of coral-reef shark depletion? Biol Conserv 176:39–47 Robbins WD, Hisano M, Connolly SR, Choat JH (2006) Ongoing collapse of coral-reef shark populations. Curr Biol 16:2314–2319 Robbins WD, Renaud P (2016) Foraging mode of the grey reef shark Carcharhinus amblyrhynchos under two different scenarios. Coral Reefs 35:253–260 Roff G, Doropoulos C, Rogers A, Bozec YM, Krueck NC, Aurellado E, Priest M, Birrell C, Mumby PJ (2016) The ecological role of sharks on coral reefs. Trends Ecol Evol 31:395–407 Ross ST (1986) Resource partitioning in fish assemblages: a review of field studies. Copeia 1986:352–388 Ruppert JLW, Travers MJ, Smith LL, Fortin MJ, Meekan MG (2013) Caught in the middle: combined impacts of shark removal and coral loss on the fish communities of coral reefs. PLoS ONE 8:e74648 Salini J, Blaber S, Brewer D (1992) Diets of sharks from estuaries and adjacent waters of the north-eastern Gulf of Carpentaria, Australia. Mar Freshw Res 43:87–96 Sherman CS, Simpfendorfer CA, Pacoureau N, Matsushiba JH, Yan HF, Walls RHL, Rigby CL, VanderWright WJ, Jabado RW, Pollom RA, Carlson JK, Charvet P, Bin Ali A, Fahmi, Cheok J, Derrick DH, Herman KB, Finucci B, Eddy TD, Palomares MLD, Avalos-Castillo CG, Kinattumkara B, Blanco-Parra MP, Dharmadi, Espinoza M, Fernando D, Haque AB, Mejía-Falla PA, Navia AF, Pérez-Jiménez JC, Utzurrum J, Yuneni RR, Dulvy NK (2023) Half a century of rising extinction risk of coral-reef sharks and rays. Nat Commun 14:15 Simpfendorfer CA, Heupel MR, Hueter RE (2002) Estimation of short-term centres of activity from an array of omnidirectional hydrophones and its use in studying animal movements. Can J Fish Aquat Sci 59:23–32 Speed CW, Meekan MG, Field IC, McMahon CR, Stevens JD, McGregor F, Huveneers C, Berger Y, Bradshaw CJA (2011) Spatial and temporal movement patterns of a multi-species coastal reef shark aggregation. Mar Ecol Prog Ser 429:261–275 Speed CW, Meekan MG, Field IC, McMahon CR, Abrantes K, Bradshaw CJA (2012) Trophic ecology of reef sharks determined using stable isotopes and telemetry. Coral Reefs 31:357–367 Speed CW, Meekan MG, Field IC, McMahon CR, Stevens JD, McGregor F, Huveneers C, Berger Y, Bradshaw CJA (2011) Spatial and temporal movement patterns of a multi-species coastal reef shark aggregation. Mar Ecol Prog Ser 429:261–275 Speed CW, Rees MJ, Cure K, Vaughan B, Meekan MG (2019) Protection from illegal fishing and shark recovery restructures mesopredatory fish communities on a coral reef. Ecol Evol 9:10553–10566 Tilley A, López-Angarita J, Turner JR (2013) Diet reconstruction and resource partitioning of a Caribbean marine mesopredator using stable-isotope Bayesian modelling. PLoS ONE 8:e79560 Truchy A, Göthe E, Angeler DG, Ecke F, Sponseller RA, Bundschuh M, Johnson RK, McKie BG (2019) Partitioning spatial, environmental and community drivers of ecosystem functioning. Landsc Ecol 34:2371–2384 Udyawer V, Dwyer RG, Hoenner X, Babcock RC, Brodie S, Campbell HA, Harcourt RG, Huveneers C, Jaine FRA, Simpfendorfer CA, Taylor MD, Heupel MR (2018) A standardised framework for analysing animal detections from automated tracking arrays. Anim Biotelem 6:17 van Zinnicq Bergmann MPM, Griffin LP, Bodey TW, Guttridge TL, Aarts G, Heithaus MR, Smukall MJ, Papastamatiou YP (2024) Intraguild processes drive space-use patterns in a large-bodied marine predator community. J Anim Ecol 93:876–890 Vianna GMS, Meekan MG, Meeuwig JJ, Speed CW (2013) Environmental influences on patterns of vertical movement and site fidelity of grey reef sharks ( Carcharhinus amblyrhynchos ) at aggregation sites. PLoS ONE 8:e60331 Watsky MA, Gruber SH (1990) Induction and duration of tonic immobility in the lemon shark Negaprion brevirostris . Fish Physiol Biochem 8:207–210 Williams LH, Anstett A, Bach Muñoz V, Chisholm J, Fallows C, Green JR, Higuera-Rivas JE, Skomal G, Winton M, Hammerschlag N (2021) Sharks as exfoliators: widespread chafing between marine organisms suggests an unexplored ecological role. Ecology 102:e03570 Williamson MJ, Tebbs EJ, Dawson TP, Jacoby DMP (2019) Satellite remote sensing in shark and ray ecology, conservation and management. Front Mar Sci 6:135 Wilson BR (2013) The biogeography of the Australian North West Shelf: environmental change and life’s response. Geological Society of London, Memoir 38 Wirsing AJ, Heithaus MR, Dill LM (2007a) Can you dig it? Use of excavation, a risky foraging tactic, by dugongs is sensitive to predation danger. Anim Behav 74:1085–1091 Wirsing AJ, Heithaus MR, Dill LM (2007b) Fear factor: do dugongs ( Dugong dugon ) trade food for safety from tiger sharks ( Galeocerdo cuvier )? Oecologia 153:1031–1040 Wright A, Dalzell PJ, Richards AH (1986) Some aspects of the biology of the red bass Lutjanus bohar (Forsskål) from the Tigak Islands, Papua New Guinea. J Fish Biol 28:533–544 Supplementary Files DehneMarineBiologySupplementaryInformation.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 05 Dec, 2025 Reviewers invited by journal 02 Dec, 2025 Editor assigned by journal 27 Nov, 2025 First submitted to journal 25 Nov, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8209051","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":554201264,"identity":"9034e824-33d7-48ac-a5ef-6bed7e939705","order_by":0,"name":"Laura-Marie Dehne","email":"data:image/png;base64,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","orcid":"https://orcid.org/0009-0001-2008-5748","institution":"UWA: University of Western Australia","correspondingAuthor":true,"prefix":"","firstName":"Laura-Marie","middleName":"","lastName":"Dehne","suffix":""},{"id":554201265,"identity":"a1f12908-b5a9-46f4-80f4-b6a0cdce9ed2","order_by":1,"name":"Luciana C. Ferreira","email":"","orcid":"","institution":"Australian Institute of Marine Science","correspondingAuthor":false,"prefix":"","firstName":"Luciana","middleName":"C.","lastName":"Ferreira","suffix":""},{"id":554201266,"identity":"50488721-1fda-46da-91c7-5f9e6785985e","order_by":2,"name":"Conrad Speed","email":"","orcid":"","institution":"Australian Institute of Marine Science","correspondingAuthor":false,"prefix":"","firstName":"Conrad","middleName":"","lastName":"Speed","suffix":""},{"id":554201267,"identity":"6b1f54ed-a5fe-4ca7-9a36-fdc70e16b423","order_by":3,"name":"Robert Harcourt","email":"","orcid":"","institution":"Macquarie University","correspondingAuthor":false,"prefix":"","firstName":"Robert","middleName":"","lastName":"Harcourt","suffix":""},{"id":554201268,"identity":"90604d3b-f91b-449d-b3fd-57ac07a8f47e","order_by":4,"name":"Ben D’Antonio","email":"","orcid":"","institution":"Shark Research Foundation","correspondingAuthor":false,"prefix":"","firstName":"Ben","middleName":"","lastName":"D’Antonio","suffix":""},{"id":554201269,"identity":"0a837b77-65b2-4baa-916a-071832f5b60a","order_by":5,"name":"Mark Meekan","email":"","orcid":"","institution":"The University of Western Australia","correspondingAuthor":false,"prefix":"","firstName":"Mark","middleName":"","lastName":"Meekan","suffix":""}],"badges":[],"createdAt":"2025-11-26 06:01:37","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8209051/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8209051/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":97412155,"identity":"6bd27c6b-ef10-4186-a029-ae4fd1e14d06","added_by":"auto","created_at":"2025-12-04 05:52:47","extension":"xml","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":9390,"visible":true,"origin":"","legend":"","description":"","filename":"mabiMABID2500624.xml","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/5c3eca62007d6e17d5dda199.xml"},{"id":97412153,"identity":"192615de-6052-4f56-bb1c-3f1a029eade9","added_by":"auto","created_at":"2025-12-04 05:52:47","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1021,"visible":true,"origin":"","legend":"","description":"","filename":"MABID250062414743.go.xml","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/3c0cc029ddf31a628aa6ac26.xml"},{"id":97666665,"identity":"96f83721-ebc7-4154-acbd-ddfb3d8f99da","added_by":"auto","created_at":"2025-12-08 09:21:50","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":775,"visible":true,"origin":"","legend":"","description":"","filename":"MABID2500624Import.xml","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/bd95e29e677d4918f0378414.xml"},{"id":97667331,"identity":"c1982b6c-1054-4209-a146-8d388c333fa0","added_by":"auto","created_at":"2025-12-08 09:23:15","extension":"xml","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":178841,"visible":true,"origin":"","legend":"","description":"","filename":"MABID25006240enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/500a45560f1028671e32516c.xml"},{"id":97412158,"identity":"d99979c0-4143-43b3-b09a-bd0cc49332eb","added_by":"auto","created_at":"2025-12-04 05:52:50","extension":"png","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":56394,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/6e309c4fbdfb746004cd5cf2.png"},{"id":97412140,"identity":"d397c806-5506-49c2-8d1b-dcfd46c5359f","added_by":"auto","created_at":"2025-12-04 05:52:45","extension":"png","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":75780,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/91895aa56dbc25f8d27b6cf5.png"},{"id":97412156,"identity":"70ae4831-2b0b-4a3b-b021-74a4c2a87d55","added_by":"auto","created_at":"2025-12-04 05:52:49","extension":"png","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":78617,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/4e5feda9c7f10bf66d473e10.png"},{"id":97666673,"identity":"2b0e161d-fabb-4166-83b0-0172c811bfe6","added_by":"auto","created_at":"2025-12-08 09:21:50","extension":"png","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":140403,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/fe786c29754d491814ef4c27.png"},{"id":97667323,"identity":"218977e8-4fc8-4b09-bb83-caaf34eec79a","added_by":"auto","created_at":"2025-12-08 09:23:15","extension":"emf","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":5257408,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage5.emf","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/e405899fce5c9740625695a4.emf"},{"id":97666247,"identity":"8979611d-11d0-4678-bd48-fc5590cf774b","added_by":"auto","created_at":"2025-12-08 09:20:42","extension":"emf","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":5527928,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage6.emf","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/4672719b7e9d07a64b8759ba.emf"},{"id":97666256,"identity":"45fbfb04-956b-4eef-9d40-eaa6baa3ecf3","added_by":"auto","created_at":"2025-12-08 09:20:43","extension":"png","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":15523,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/a3d2b4ccbe0a3dbdc38e99e2.png"},{"id":97412142,"identity":"96d7cbef-5d66-4b01-8637-047eb838bb9e","added_by":"auto","created_at":"2025-12-04 05:52:46","extension":"png","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":20003,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/5c6275975e70b293d015daab.png"},{"id":97666731,"identity":"cb595e93-9a41-41b5-a499-d71b6d2a3de4","added_by":"auto","created_at":"2025-12-08 09:22:01","extension":"png","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":21021,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/091fe599d1dfa9616dd55bc9.png"},{"id":97666720,"identity":"cf07b3eb-9325-4933-8ca5-a88cfd1a3606","added_by":"auto","created_at":"2025-12-08 09:21:57","extension":"png","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":30464,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/3b13f1c63f85b4df0f45e918.png"},{"id":97666807,"identity":"e8091b2b-0a5e-4bc4-94dc-fc3edd6c0c07","added_by":"auto","created_at":"2025-12-08 09:22:10","extension":"png","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":90444,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/ddd400dffbe8a14a25167d81.png"},{"id":97412157,"identity":"b227c5da-76ae-41e4-b35c-6396860f1dfa","added_by":"auto","created_at":"2025-12-04 05:52:49","extension":"png","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":75242,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/82daae08b1427886d27c67f0.png"},{"id":97412145,"identity":"876e4450-b7b5-4061-9a66-c0b18f27d220","added_by":"auto","created_at":"2025-12-04 05:52:46","extension":"xml","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":174964,"visible":true,"origin":"","legend":"","description":"","filename":"MABID25006240structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/30834355131b02fc7ac76835.xml"},{"id":97412149,"identity":"034825f5-3efb-44cf-aea8-deb9f5ba102a","added_by":"auto","created_at":"2025-12-04 05:52:46","extension":"html","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":182631,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/533b955fee3ddea5ab6a7ffb.html"},{"id":97412133,"identity":"88a8e36c-829f-45da-9e78-b89203deb772","added_by":"auto","created_at":"2025-12-04 05:52:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":56394,"visible":true,"origin":"","legend":"\u003cp\u003eNumber of individuals per size category of red bass (a) and grey reef sharks (b). Turquoise bars Rowley Shoals and purple bars the Scott Reefs. NA: not annotated.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/b084a952c843165d60109004.png"},{"id":97666553,"identity":"e28aa976-7861-48d1-9806-3d973a405494","added_by":"auto","created_at":"2025-12-08 09:21:31","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":75780,"visible":true,"origin":"","legend":"\u003cp\u003eMonthly detections of red bass (a) at the Rowley Shoals, (b) at the Scott Reefs, and grey reef sharks at (c) the Rowley Shoals and (d) the Scott Reefs. Orange-coloured bars are Austral summer months, blue-coloured bars Austral winter months and apricot-coloured bars spring and autumn.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/f5f026406e8ce5ed0c152854.png"},{"id":97412134,"identity":"0075c0e8-bd37-4762-b655-d510b91de0ec","added_by":"auto","created_at":"2025-12-04 05:52:45","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":78617,"visible":true,"origin":"","legend":"\u003cp\u003eHourly detections for red bass at the (a) Rowley Shoals and the (b) Scott Reefs and grey reef sharks at the (c) Rowley Shoals and (d) Scott Reefs. Yellow-coloured bars indicate detections during daytime and blue-coloured bars indicate night-time detections.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/9de6985c76282e39f8d465d1.png"},{"id":97412136,"identity":"76f65252-dc27-429f-8539-e479e3157b62","added_by":"auto","created_at":"2025-12-04 05:52:45","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":140403,"visible":true,"origin":"","legend":"\u003cp\u003eResidency index (the ratio between the total number of days detected and the overall number of days in the receiver array) for each individual (tag id) red bass (a) at the Rowley Shoals and (b) the Scott Reefs, and grey reef shark at (c) the Rowley Shoals, and (d) the Scott Reefs.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/57ccda89e61b95b9058b4f7e.png"},{"id":97412138,"identity":"fe608dd5-5cfd-4110-b26d-cbe37f12e502","added_by":"auto","created_at":"2025-12-04 05:52:45","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":890592,"visible":true,"origin":"","legend":"\u003cp\u003eOverlaid shapefiles of Minimum Convex Polygon (MCP) and 50% and 95% Kernel Utilization Distributions (KUD) of red bass at (a) the Rowley Shoals, (b) the Scott Reefs, and grey reef sharks at (c) the Rowley Shoals, and (d) the Scott Reefs, displayed in QGIS.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/a0256f45f02149cf9d28b967.png"},{"id":97412154,"identity":"73f2968c-510a-42d5-8f70-7f75826d4184","added_by":"auto","created_at":"2025-12-04 05:52:47","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":820702,"visible":true,"origin":"","legend":"\u003cp\u003eOverlap of (a) 50% Kernel Utilization Distributions (KUD) of red bass (purple) and grey reef sharks (rose) at the Rowley Shoals, (b) 95% KUD of red bass (green) and grey reef sharks (yellow) at the Rowley Shoals, (c) 50% KUD of red bass (purple) and grey reef sharks (rose) at the Scott Reefs, and (d) 95% KUD of red bass (green) and grey reef sharks (yellow) at the Scott Reefs, displayed in QGIS.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/2e897429dc0b1d7cabbc2df7.png"},{"id":97677329,"identity":"04185251-a291-4600-adc2-1a81073b410f","added_by":"auto","created_at":"2025-12-08 09:52:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2585885,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/3ae0538c-3898-4de9-af9d-9656c81becaa.pdf"},{"id":97412152,"identity":"82448c68-a218-4a33-8251-1269794a83ca","added_by":"auto","created_at":"2025-12-04 05:52:46","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":17846972,"visible":true,"origin":"","legend":"","description":"","filename":"DehneMarineBiologySupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-8209051/v1/570c169ed76e0e5e572382ae.docx"}],"financialInterests":"","formattedTitle":"Effects of Shark Removal on Spatial Partitioning Among Large Mesopredators on Coral Reefs","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eThe coexistence of ecologically similar species is often mediated through niche partitioning, a process grounded in the ecological principle that two species competing for the same resources cannot coexist indefinitely (Gause, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1932\u003c/span\u003e; Armstrong, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1976\u003c/span\u003e; Volterra, 1927). Such partitioning may occur across spatial, temporal, or trophic dimensions, thereby facilitating the cohabitation of functionally similar species (Ross, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Truchy et al. \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). This mechanism implies that each species plays a distinct role within the ecosystem, challenging the notion of functional redundancy. Indeed, evidence from coral reef ecosystems suggests that redundancy among coexisting species is often limited (D\u0026rsquo;Agata et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Guillemot et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Mouillot et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), underscoring the ecological significance of interspecific interactions in maintaining niche structure and community dynamics (Bascompte et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Heithaus et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Paine, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1992\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eCoral reef food webs are among the most structurally complex in marine systems, with high densities of apex and mesopredators (Lucifora et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Pimiento et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Despite the prevalence of predators, the mechanisms underlying their coexistence, particularly through spatial or temporal niche partitioning, remains poorly understood (van Zinnicq Bergmann et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). This knowledge gap is concerning, given that many large reef predators are heavily targeted by fisheries, contributing to their decline. Fishing pressure disproportionately affects large-bodied species, and global studies indicate that reef sharks, once the dominant mesopredators in these systems, are now functionally extinct on one-fifth of the world\u0026rsquo;s coral reefs (MacNeil et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Their loss can disrupt trophic dynamics and reshape interactions among lower-order predators (Barley et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017b\u003c/span\u003e, Meekan et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2025\u003c/span\u003e, Sherman et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eTwo prominent mesopredators found across Indo-Pacific coral reefs are grey reef sharks (\u003cem\u003eCarcharhinus amblyrhynchos\u003c/em\u003e) and red bass (\u003cem\u003eLutjanus bohar\u003c/em\u003e). Both are large-bodied, nocturnally active predators that share similar dietary preferences, including fish, cephalopods, and benthic invertebrates (Chin et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Frisch et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Barley et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e). Grey reef sharks can attain up to 1.8 meters in length (Chin et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) and are typically associated with outer reef slopes and channels (Rizzari et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Red bass, although smaller (typically 60 cm), are a large reef-dwelling teleost predator and frequently occupy similar habitats to grey reef sharks but display more restricted movements (Ferreira et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The apparent overlap in their ecological niches raises questions about the mechanisms facilitating their coexistence in nutrient-limited coral reef environments (Grigg et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1984\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAlthough these species co-occur, finer-scale partitioning, either temporally or spatially, may be needed to reduce direct competition. Acoustic telemetry, which uses arrays of submerged receivers to track tagged animals, is a powerful tool for studying such patterns of spatial ecology (Hussey et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Mourier et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; van Zinnicq Bergmann et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). This technology allows researchers to investigate spatial and temporal patterns of movement simultaneously across multiple species (Speed et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Williams et al. 2022). For example, acoustic telemetry combined with network analysis have shown that the movement patterns of grey reef sharks support much greater connectivity within a coral reef system than red bass movement, which generate strong, but localised connectivity (Ferreira et al \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). A unique natural experiment off the northwest coast of Western Australia offers insight into how local-scale pressures might influence niche dynamics. Here, the Rowley Shoals, designated as a no-take marine protected area for over three decades, supports intact populations of reef sharks and mesopredatory teleosts (Speed et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In contrast, a neighbouring reef system in the region called the Scott Reefs are subject to artisanal shark fishing by Indonesian fishers using longlines, an activity permitted under traditional access rights (Ruppert et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The differential fishing pressure across these reef systems provides an opportunity to examine whether reduced shark populations alter spatial dynamics and interactions among co-occurring mesopredators. Previous studies in these systems have shown that declines in shark abundance correspond with shifts in mesopredator diet, condition, and community structure (Barley et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003eb\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eHere, we test whether grey reef sharks and red bass exhibit spatial and/or temporal partitioning on coral reefs, and whether such partitioning is influenced by the relative abundance and size structure of these predators. We hypothesise that any spatial or temporal partitioning will be more pronounced in the more protected system of the Rowley Shoals, where larger reef sharks potentially outcompete or predate on red bass. In the fished system of the Scott Reefs, we expect more spatial and temporal overlap due to the absence or reduced abundance of larger reef sharks. Understanding these dynamics can help inform conservation strategies and improve our comprehension of predator interactions in coral reef ecosystems and provide insight into how the loss of these predators may affect overall ecosystem function.\u003c/p\u003e"},{"header":"2. METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Study site\u003c/h2\u003e\u003cp\u003eThe Rowley Shoals and the Scott Reefs are located at the north-western continental shelf off Australia, approximately 400 km from the coast (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). These reef systems form part of the shelf-edge atoll complex on Australia\u0026rsquo;s north-west continental margin, rising steeply from deep water and exhibiting similar geomorphological and oceanographic conditions (Wilson \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), providing a broadly comparable habitat template for fish and shark assemblages. Since 1990, the Rowley Shoals have been protected under various management regimes, with the lagoons of Imperieuse and Clerke Reef designated as no-take zones where all fishing is prohibited by the Western Australian Government (Department of Environment and Conservation 2006) and thus can be considered a somewhat \u0026ldquo;pristine\u0026rdquo; coral reef environment. In contrast, the Scott Reefs have a longstanding history of fishing activities, notably shark fishing by artisanal Indonesian fishers, a practice permitted by Australia in acknowledgement of traditional access to the reef that dates back many centuries (Environment Australia \u0026amp; Natural Heritage Trust, 2002; Edgar et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Acoustic tracking data\u003c/h2\u003e\u003cp\u003eThe study used an existing acoustic telemetry dataset, freely available from the Integrated Marine Observing System-Animal Tracking Facility, accessible through the AODN portal (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://portal.aodn.org.au/\u003c/span\u003e\u003cspan address=\"https://portal.aodn.org.au/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003e)\u003c/span\u003e (Hoenner et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). This dataset included acoustic tracking data for 63 grey reef sharks (\u003cem\u003eCarcharhinus amblyrhynchos\u003c/em\u003e) and 25 red bass (\u003cem\u003eLutjanus bohar\u003c/em\u003e) detected by acoustic receiver arrays in the Rowley Shoals and the Scott Reefs. Red bass were tagged at both reef systems in 2015, whereas grey reef sharks were tagged over multiple years (2007, 2011, 2012 at the Rowley Shoals, and in 2011 at the Scott Reefs), with some temporal overlap between datasets (Figure S3, Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The animals were equipped with InnovaSea V16 transmitters (for sharks) and V13 transmitters (for smaller sharks and red bass), with their movements monitored by arrays of passive acoustic receivers anchored to the seabed (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e b, c). These receivers are designed to log data when tagged animals enter their listening radius, which is typically around 300\u0026ndash;500 m (Heupel et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Tagging occurred at various shallow sites (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e d, e) strategically located near the reef crest and within the reef lagoons (Field et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). For details of the tagging techniques for grey reef sharks, see Field et al. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Briefly, grey reef sharks were caught by hook and line, brought to the surface, and secured dorsal surface down against a boat to induce tonic immobility (Field et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The sharks were sexed, measured and a small incision made for insertion of an acoustic tag in the abdominal cavity. The incision was then sutured closed, and the shark was released. This process generally took less than 15 minutes. Similarly, red bass were also tagged after capture by hook and line. Fish were landed on the vessel and held in a tank containing the anaesthetic Aqui-S. Once unconscious, the fish were held in a cradle and a tag inserted via a small incision in the abdomen. The cut was sutured closed, and the fish returned to a tank for recovery. After around 2 hours the fish were released.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Data analysis\u003c/h2\u003e\u003cp\u003eThe acoustic telemetry dataset was analysed using RStudio Version 2023.03.1\u0026thinsp;+\u0026thinsp;446 and QGIS Version 3.26.3 \u0026ndash; Buenos Aires. For the Rowley Shoals, which consists of three atolls separated by 28\u0026ndash;44 km, the analysis specifically focused on Clerke Reef, the middle atoll (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), as red bass were exclusively tagged at this location and did not move among atolls. At Scott Reefs, the analysis encompassed both North and South Scott reefs due to their proximity to each other (~\u0026thinsp;6 km), facilitating movement between the adjacent reefs. The receiver array at the Rowley Shoals and the Scott Reefs varied in size and number, requiring us to normalise detections by the number of receivers at each location.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Movement metrics\u003c/h2\u003e\u003cp\u003eMovement and habitat use metrics were calculated for each species at each reef system separately to allow comparisons between species and within and between reef systems. The number of detections received from tagged animals for each species and each reef system was used to identify preferred areas (90% of detection data). Abacus plots were created to visually inspect detection frequencies over time for each tagged individual during the operational lifespan of the tags (Kraft et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). A residency index (RI), ranging from 0 (never detected) to 1 (detected every possible day), was calculated for each individual as the ratio of days each animal was detected divided by total days the animal was detected within the acoustic array (e.g., date of last detection \u0026ndash; date of first detection), offering insights into side fidelity and movement patterns (Appert et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eCentre of Activity (COA) (Simpfendorfer et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2002\u003c/span\u003e) for each species at each reef system was estimated based on weighted means of the number of concurrent detections across receivers with overlapping ranges during a given time period. We chose a 60-minute time period using the \u0026ldquo;COA\u0026rdquo; function from the \u0026ldquo;Vtrack\u0026rdquo; package (Udyawer et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) for each tagged animal with a minimum of five locations to allow for subsequent habitat use analysis. From these COA, Minimum Convex Polygons (MCP) were calculated using the \u0026ldquo;adehabitatHR\u0026rdquo; package (Calenge, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) in the software RStudio Version 2023.03.1\u0026thinsp;+\u0026thinsp;446, which delineates the smallest area encompassing all locations representing the minimal areas used by each individual. Kernel Utilisation Distributions (KUDs) were also calculated using the \u0026ldquo;adehabitatHR\u0026rdquo; package. The \u0026ldquo;kernelUD\u0026rdquo; function fits a bivariate probability density function to the location data (here we used the location of the COA), using the kernel smoothing parameter \u0026ldquo;href\u0026rdquo; (Kie, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), which we selected to ensure contiguous rather than disjoint utilisation distributions. However, because \u0026ldquo;href\u0026rdquo; is very sensitive to sample size, it may have resulted in inflated utilisation distributions, particularly during periods of low detection. To minimise potential biases from these inflated KUD metrics, we focused our overlap analyses on percentage-based comparisons rather than absolute area values.\u003c/p\u003e\u003cp\u003eRange testing was not conducted when the receivers were deployed, therefore we used a conservative detection range of 300 m (Kessel et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). The areas of the 50% and 95% kernel utilisation distributions (KUD) were calculated for each individual but also for each species using all the locations for all individuals of a species in each reef system. Temporal patterns in space use were analysed by segmenting data into monthly, diurnal and nocturnal periods, and further into hourly intervals.\u003c/p\u003e\u003cp\u003eShapefiles from 50% and 95% KUDs were overlaid in QGIS and the overlap in area (km\u003csup\u003e2\u003c/sup\u003e) between the utilisation distributions of red bass and grey reef sharks at both reef systems calculated in R. This analysis was done for each species combined at each reef system and for diurnal and nocturnal periods.\u003c/p\u003e\u003cp\u003eIn our spatial analysis of red bass we encountered significant challenges due to scattered detection patterns and sparse data, particularly during non-peak hours. This sparsity of data precluded the use of Brownian bridges for estimating movement paths (Horne et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) and limited the calculations of MCPs and KUDs.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. RESULTS","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Size and detections at receivers\u003c/h2\u003e\u003cp\u003eTagged red basshad an average total length of 58.7 cm\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8 at the Rowley Shoals and 48.8 cm\u0026thinsp;\u0026plusmn;\u0026thinsp;16.0 at the Scott Reefs (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Tagged grey reef sharks had a mean total length of 146.1 cm\u0026thinsp;\u0026plusmn;\u0026thinsp;19.5 at the Rowley Shoals and 131.1 cm \u0026plusmn; 30.7 at the Scott Reefs. Both red bass and grey reef sharks tended to be larger at the Rowley Shoals than Scott Reefs (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Kolmogorov-Smirnov test p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTagged animals were detected on 27 of the 41 receivers deployed at the Rowley Shoals and on all 18 receivers deployed at the Scott Reefs (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Red bass were detected 43,627 times at the Rowley Shoals and 1,863 times at the Scott Reefs. At the Rowley Shoals, 90% of red bass detections were recorded by just four receivers, with detections spanning a total of 22 receivers (Figure S2a, Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). At the Scott Reefs, 90% of detections occurred on three receivers, with detections recorded across eight receivers in total (Figure S2b, Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Grey reef sharks had a higher number of detections than red bass, with 409,626 detections dispersed across 27 receivers at the Rowley Shoals (Clerke Reef only), of which 90% were recorded by 15 receivers (Figure S2c, Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). At the Scott Reefs, grey reef sharks were detected 241,233 times across all 18 receivers, with 90% of detections concentrated on three receivers (Figure S2d, Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Mean detections per receiver were 1,983\u0026thinsp;\u0026plusmn;\u0026thinsp;3,656 and 233\u0026thinsp;\u0026plusmn;\u0026thinsp;449 for red bass, and 15,117\u0026thinsp;\u0026plusmn;\u0026thinsp;12,546 and 13,402\u0026thinsp;\u0026plusmn;\u0026thinsp;34,044 for grey reef sharks at the Rowley Shoals and Scott Reefs, respectively (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Two of the three receivers most frequented by red bass were also those that recorded the most detections of tagged sharks at the Scott Reefs (Figure S2b, d). In contrast, at the Rowley Shoals, the five receivers that detected tagged red bass most frequently were not among those most used by sharks (Figure S2a, c).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Monthly detections\u003c/h2\u003e\u003cp\u003eRed bass detections were highest from April (tagging) to August at both locations, followed by a sharp decline in September (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea, b). At Rowley Shoals, detections dropped from \u0026gt;\u0026thinsp;6,000 during the first month to \u0026gt;\u0026thinsp;5,000 per month until August, whereas at the Scott Reefs, they declined from \u0026gt;\u0026thinsp;500 to 200\u0026ndash;400 for the subsequent months until a sharp decline in September (\u0026lt;\u0026thinsp;100). For grey reef sharks, the frequency of detections was more consistent throughout the year at both reef systems (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec, d). The highest number of detections occurred in October (tagging occurred in September and December) at the Rowley Shoals (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec), and more detections were recorded in December (tagging) and January at the Scott Reefs (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Hourly detections\u003c/h2\u003e\u003cp\u003eAt both the Rowley Shoals and the Scott Reefs, the number of detections of red bass increased throughout the day and into the evening, after a low in early morning hours (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, b). Patterns in detections at the Scott Reefs were more variable on an hour-to-hour basis than at the Rowley Shoals (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFor grey reef sharks, the detection frequency was more consistent throughout the day in both reef systems (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec, d), although the highest number of detections occurred from 20\u0026ndash;22.00 hrs (\u0026gt;\u0026thinsp;20,000 detections) at the Rowley Shoals (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec), and peaked both around midday and at 22.00 hrs (~\u0026thinsp;12,000 detections) at the Scott Reefs (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Site fidelity\u003c/h2\u003e\u003cp\u003eThere was high variability in detection frequencies among individual red bass and grey reef sharks at both the Rowley Shoals and the Scott Reefs (Figure S3). At the Rowley Shoals, the data for red bass spanned from May 2015 to September 2016, with three individuals resident within the array, three individuals ceasing transmission after a few weeks and most others recording very regularly dispersed detections, that included simultaneous gaps in the data during June and July of both years (Figure S3a). Red bass were tracked at the Scott Reefs from April 2015 to September 2016 (Figure S3b). Although detection frequencies also varied among individual red bass, there were less synchronous patterns among individuals (Figure S3a, b) at Scott Reefs than at the Rowley Shoals.\u003c/p\u003e\u003cp\u003eGrey reef sharks were tagged in December 2007 and September 2011 at the Rowley Shoals. After the first deployment of tags, sharks were detected from December 2007 to November 2008 (Figure S3c) and in the second deployment they were detected from September 2011 to February 2016 in (Figure S3d). In both of these periods, patterns of residency were very similar, with most tagged sharks (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;31) exhibiting nearly constant patterns of detection over long periods (Figure S3c, d), with only four sharks ceasing transmission after two to four months (Figure S3c, d). At the Scott Reefs, grey reef sharks were tagged in December 2011 and were detected by the receiver array until May 2016 when the receiver array was removed (Figure S3e). Only one shark ceased transmission after more than six months. Sharks displayed detection patterns that ranged from resident to intermittent (Figure S3e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.5. Residency\u003c/h2\u003e\u003cp\u003eAt the Rowley Shoals, individual red bass exhibited variable patterns of residency indices ranging from very high (residency index\u0026thinsp;\u0026gt;\u0026thinsp;0.75) to very low (residency index\u0026thinsp;\u0026lt;\u0026thinsp;0.1) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). This pattern was similar for red bass at the Scott Reefs, with one individual displaying a residency index\u0026thinsp;\u0026gt;\u0026thinsp;0.75 and four red bass displaying almost no residency in the array (residency index\u0026thinsp;\u0026lt;\u0026thinsp;0.1) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). In contrast, most grey reef sharks at the Rowley Shoals had relatively high residency within the array, with 21 individuals having residency indices\u0026thinsp;\u0026gt;\u0026thinsp;0.5 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec), and 10 with very high residency (residency index\u0026thinsp;\u0026gt;\u0026thinsp;0.75). Similarly, at the Scott Reefs, grey reef sharks also had higher residency indices overall (6 individuals with residency index\u0026thinsp;\u0026gt;\u0026thinsp;0.5) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed) than red bass. Statistical analysis further supports these observations, and the Wilcoxon Rank Sum Test revealed a significant difference in the residency indices between red bass and grey reef sharks \u003cem\u003e(p\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0088), suggesting that grey reef sharks exhibited stronger or more consistent residency patterns at both locations. Bootstrap confidence intervals for the mean residency indices (95% CI for red bass: 0.1992 to 0.4535; grey reef sharks: 0.4352 to 0.5905) further indicated that on average, grey reef sharks had higher residency indices than red bass.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.6. Spatial distribution\u003c/h2\u003e\u003cp\u003eMinimum Convex Polygon (MCP) for all detections of red bass at the Rowley Shoals covered an area of 13.95 km\u0026sup2;, delimited by 26 receivers (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, Tables S1, S2). This area included receivers both inside and outside the lagoon at Clerke Reef. The most distant receivers were located on the fore reef, one approximately 4 km north of the channel and another near the reef crest about 9.4 km to the south (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). The MCP for all detections of red bass at the Scott Reefs covered an area of 8.84 km\u0026sup2;, delimited by 8 receivers (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, Tables S1, S2). The MCP only encompassed receivers at North Scott but included areas both inside and outside the lagoon. The furthest receiver was located on the fore reef, 6 km south of the channel on the reef crest (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe 95% Kernel Utilisation Distribution (KUD) for all detections of red bass at the Rowley Shoals identified three areas. A large area stretched from inside the lagoon along the channel and around the reef crest, with two smaller areas positioned north of the channel along the reef crest (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). Together these encompassed an area of 3 km\u003csup\u003e2\u003c/sup\u003e (Table S2). In contrast, the 95% KUD for red bass at the Scott Reefs included two extended areas. The first, smaller area was located inside the lagoon, whereas the second extended outside the channel along the reef crest (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). Together, these encompassed an area of 2.77 km\u003csup\u003e2\u003c/sup\u003e (Table S2).\u003c/p\u003e\u003cp\u003eAt the Rowley Shoals, the 50% KUD for all detections of red bass included three small core areas, two of which were located inside the lagoon, and a third, more elongated area, extended outside the channel along the reef crest (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). These encompassed an area of 0.38 km\u0026sup2; (Table S2), smaller than the corresponding area at the Scott Reefs (Table S2). The 50% KUD for red bass at the Scott Reefs included one small core area, located just outside the channel (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb), encompassing an area of 0.44 km\u0026sup2; (Table S2), which was slightly larger than the area of the KUD of the species at the Rowley Shoals.\u003c/p\u003e\u003cp\u003eGrey reef sharks exhibited larger areas of MCPs and KUDs than red bass (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, d, Table S2). The MCP for grey reef sharks at the Rowley Shoals covered an area of 14.57 km\u003csup\u003e2\u003c/sup\u003e, delimited by 27 receivers (Table S2). This included areas inside and outside the lagoon, with the most distant receivers located in the fore reef around 4 km north of the channel around the reef crest and about 9.4 km south of the channel (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec). At the Scott Reefs, the MCP for all detections of grey reef sharks spanned a large area of 214.94 km\u003csup\u003e2,\u003c/sup\u003e delimited by 18 receivers (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed, Tables S1, S2). This MCP included receivers positioned inside and outside the lagoon, north of the channel, as well as in the south of North Scott and South Scott Reef, with the furthest receiver located in the fore reef about 6 km north of the channel around the reef crest and approximately 18 km south of the channel, near the edge of South Scott (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed).\u003c/p\u003e\u003cp\u003eThe 95% KUD for grey reef sharks at the Rowley Shoals had four extended areas, the largest spanning from inside the lagoon, along the channel, and around the reef crest, and three smaller areas, two located north of the channel and one south of the channel along the reef crest (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec). These totalled an area of 4.89 km\u003csup\u003e2\u003c/sup\u003e (Table S2). At the Scott Reefs, the 95% KUD for grey reef sharks was smaller than at the Rowley Shoals, with a single area located just outside the channel (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed), encompassing 3.15 km\u003csup\u003e2\u003c/sup\u003e (Table S2).\u003c/p\u003e\u003cp\u003eThe 50% KUD for grey reef sharks at the Rowley Shoals consisted of four smaller core areas, one located inside the lagoon, another elongated area directly in front of the channel and two further north along the reef crest (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec), with a total area of 1.25 km\u003csup\u003e2\u003c/sup\u003e (Table S2). The 50% Kernel Utilisation Distribution (KUD) at this reef system had one core area, located just in front of the channel (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed) and encompassing an area of 0.64 km\u003csup\u003e2\u003c/sup\u003e (Table S2). Overall, the 50% Kernel utilisation distributions for both species at both reef systems occurred near the channel, inside the lagoon and outside the fore reef.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.7. Monthly spatial distribution\u003c/h2\u003e\u003cp\u003eFor red bass, the monthly analysis of residency was limited to MCPs due to the low number of detections in some months (Figures S4, S5), variations in number of detected individuals in some months (Figure S5, Table S3, S4), individual variability (Table S7), and large gaps in the data (Figure S3). This prevented the calculation of monthly KUDs for the species. The MCP analysis revealed that red bass occupied a larger area between March and May at both reef systems (Figure S5a, S5b), with a marked reduction in space use during the remainder of the year.\u003c/p\u003e\u003cp\u003eIn contrast, grey reef sharks were detected by a relatively consistent number of receivers throughout the year (Figure S4, S5, Table S5, S6), allowing for the calculation of both MCP and KUD metrics on a monthly basis. The spatial metrics for grey reef sharks at the Rowley Shoals indicated consistent space use year-round, although a noticeable decrease in area of the MCP occurred between November and January. This reduction in area did not occur in the 95% and 50% KUDs (Figure S5c). At the Scott Reefs, although the MCP areas showed large fluctuations over the year, the areas for the 95% and 50% KUDs remained relatively constant (Figure S5d).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.8. Diel spatial distribution\u003c/h2\u003e\u003cp\u003eDuring the day, the 95% KUD for red bass at the Rowley Shoals encompassed three extended areas: one large area that spanned from inside the lagoon along the channel and around the reef crest, and two smaller areas located north of the channel along the reef crest (Figure S6a). These covered an area of 3.73 km\u003csup\u003e2\u003c/sup\u003e (Table S2). At night, the 95% KUD still identified three extended areas, but with slightly different configurations: a large area from inside the lagoon along the channel and extending to the outer channel at the reef crest, and two smaller areas, one north of the channel at the reef crest and another smaller area inside the lagoon (Figure S6b). These totalled an area of 2.72 km\u003csup\u003e2\u003c/sup\u003e (Table S2). At the Scott Reefs, the 95% KUD of red bass during the daytime had two extended areas: a smaller area inside the lagoon and another outside the channel along the reef crest (Figure S6c) that encompassed an area of 3.64 km\u003csup\u003e2\u003c/sup\u003e (Table S2). At night, the KUD was similar but slightly reduced, featuring two extended areas that closely resembled daytime patterns with one inside the lagoon and the other just outside the channel along the reef crest (Figure S6d). These covered an area of 3.01 km\u003csup\u003e2\u003c/sup\u003e (Table S2).\u003c/p\u003e\u003cp\u003eDuring the day, the 50% KUD for red bass at the Rowley Shoals identified two core areas: one just outside the channel and another inside the lagoon south of the channel (Figure S6a), which together covered an area of 0.44 km\u0026sup2; (Table S2). At night, the 50% KUD at the Rowley Shoals revealed a more fragmented pattern, with four smaller core areas: two inside the lagoon and outside the channel, one directly in front of the channel, and another slightly further south along the reef crest (Figure S6b), totalling an area of 0.36 km\u0026sup2; (Table S2). At the Scott Reefs, the daytime 50% KUD for red bass identified one core area located just outside the channel (Figure S6c), encompassing an area of 0.59 km\u0026sup2; (Table S2). Similarly, the night-time 50% KUD also identified a core area just outside the channel (Figure S6d), which was slightly smaller than during the day, measuring 0.50 km\u0026sup2; (Table S2). Both daytime and night-time core areas at the Scott Reefs were very similar in location and shape.\u003c/p\u003e\u003cp\u003eThe 95% KUD for all detections of grey reef sharks at the Rowley Shoals revealed almost identical space use during day and night. Four distinct areas were identified: a large area extending from inside the lagoon along the channel and around the reef crest, two smaller areas positioned north of the channel along the reef crest, and one area to the south of the channel (Figure S6e, f). These covered an area of 5.44 km\u003csup\u003e2\u003c/sup\u003e (Table S2). At night, the overall area of the KUD remained similar, totalling 5.48 km\u003csup\u003e2\u003c/sup\u003e (Table S2). The 95% KUD of grey reef sharks was less extensive at the Scott Reefs than the Rowley Shoals. During the day, it comprised an extended area outside the channel along the reef crest (Figure S6g) and covered an area of 4.53 km\u003csup\u003e2\u003c/sup\u003e (Table S2). At night, the 95% KUD occurred in a similar location (Figure S6h) but decreased in size to 2.97 km\u003csup\u003e2\u003c/sup\u003e (Table S2).\u003c/p\u003e\u003cp\u003eDuring the day the 50% KUD of grey reef sharks at the Rowley Shoals identified two core areas of use: one larger area stretching from inside the lagoon, through the channel, and north along the reef crest, and another located further north of the channel (Figure S6e), encompassing an area of 1.4 km\u0026sup2; (Table S2). At night, the 50% KUD formed a less continuous pattern, with four core areas: two larger areas positioned inside the lagoon and just in front of the channel, and two additional areas further north of the channel (Figure S6f). Total area of the KUD was similar to the daytime at around 1.4 km\u003csup\u003e2\u003c/sup\u003e (Table S2). At the Scott Reefs, the daytime 50% KUD of grey reef sharks covered one core area, situated just outside the channel and slightly elongated to the south (Figure S6g), with a total area of 0.84 km\u003csup\u003e2\u003c/sup\u003e (Table S2). This pattern persisted at night (Figure S6h), albeit with a slight reduction in size, resulting in a core area measuring 0.59 km\u003csup\u003e2\u003c/sup\u003e (Table S2).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.9. Overlap of space use\u003c/h2\u003e\u003cp\u003eAt the Rowley Shoals, the 50% KUD of red bass overlapped by 18.6% with the 50% KUD of grey reef sharks (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The core use areas (50% KUD) of red bass (purple; Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea) were largely separate from the core use areas of grey reef sharks (rose; Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea). In the lagoon, much of the red bass core use area did not overlap with the core use area of sharks. Outside the lagoon, sharks primarily used the northern outer reef crest while red bass concentrated around the channel and slightly south of it (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea). When considering 95% KUDs of red bass and grey reef sharks, overlap increased to 71.48% (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Both red bass and grey reef sharks used extensive areas around the lagoon and along the reef crest, extending northwards from the channel (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSpatial overlap of areas of 50% and 95% Kernel Utilization Distributions (KUD) of red bass and grey reef sharks at the Rowley Shoals and the Scott Reefs, for pooled data sets and split by day and night. The table shows the reef system, time of day (ToD), and KUD type, overlap of areas of 50% and 95% KUD of red bass with grey reef shark in km\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eReef System\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eToD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eKUD Type\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eOverlap area (km\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eOverlap red bass (%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRowley Shoals\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCombined\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e18.60\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRowley Shoals\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDay\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e17.97\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRowley Shoals\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNight\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e20.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRowley Shoals\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCombined\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e71.48\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRowley Shoals\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDay\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e70.28\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRowley Shoals\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNight\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e73.62\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eScott Reefs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCombined\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e64.28\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eScott Reefs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDay\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e68.52\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eScott Reefs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNight\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e57.99\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eScott Reefs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCombined\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e52.87\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eScott Reefs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDay\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e51.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eScott Reefs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNight\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e53.65\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAt the Scott Reefs, red bass and grey reef sharks had a higher overlap of 50% KUDs (64.28%; Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) than at the Rowley Shoals, with both species sharing the same core area just in front of the channel outside the lagoon (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec). The 95% KUDs of red bass and grey reef sharks overlapped by 52.87% (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). This lower overlap was largely due to red bass extending their use area inside the lagoon, whereas grey reef sharks extended their use area outside the channel along the outer reef crest (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e3.10. Diel overlap of space use\u003c/h2\u003e\u003cp\u003eAt the Rowley Shoals, the overlap of core areas (50% KUDs) between red bass and grey reef sharks was low, ranging between 17.97% during the day and 20.38% at night (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In contrast, the overlap of broader areas (95% KUDs) was consistently high, with 70.28% during the day and 73.63% during the night (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). At the Scott Reefs, core overlap was much higher, with 50% KUDs overlapping by 68.52% during the day and 57.99% at night. Overlap of 95% KUDs at Scott was lower overall, with 51.13% during the day and 53.65% during the night (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e"},{"header":"4. DISCUSSION","content":"\u003cp\u003eWe used acoustic telemetry to investigate spatial and temporal partitioning between red bass (\u003cem\u003eLutjanus bohar\u003c/em\u003e) and grey reef sharks (\u003cem\u003eCarcharhinus amblyrhynchos\u003c/em\u003e) within two coral reef ecosystems in northwest Australia. Given the ecological similarities and overlapping habitats of these species, we hypothesised that they might partition space at fine temporal (hours-days) and/or spatial (hundreds of meters to kilometres) scales to facilitate coexistence. Although we found little evidence for temporal partitioning, as both species were active at similar times during the diel cycles and had high residency indices, our results provided partial support for spatial partitioning. Both species were associated with key geomorphological features in both reef systems\u0026mdash;reef channels, outer reef crest, and lagoonal areas adjacent to channel mouths\u0026mdash;resulting in high overlap of 95% kernel utilisation distributions (KUDs). However, analyses of core activity spaces (50% KUDs) revealed differences in fine-scale spatial use between the species.\u003c/p\u003e\u003cp\u003eAt the Rowley Shoals, only a small part (18.6%) of the 50% KUD of red bass overlapped that of grey reef sharks, indicating that the areas of most intensive use by each species were largely distinct. In contrast, at the Scott Reefs, 64.3% of the red bass 50% KUD overlapped with that of grey reef sharks. These contrasting patterns might be explained by differences in shark abundance and size structure between reef systems. Grey reef sharks are almost three times more abundant at the unfished Rowley Shoals than at the Scott Reefs, where populations have been depleted by targeted fishing (Lester et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Moreover, surveys using baited remote underwater video systems show that at the Scott Reefs, populations of grey reef sharks are mostly composed of smaller juveniles, whereas at the Rowley Shoals, there are higher numbers of large, adult sharks (Figure S7). This disparity in size between the two species may contribute to spatial segregation at Rowley Shoals, where large adult sharks may pose a threat to red bass either through predation or interference competition. In contrast, at the Scott Reefs, smaller juvenile sharks are less likely to exclude red bass from shared habitats, resulting in greater overlap of core space use. These patterns are consistent with previous studies showing that mesopredators and prey often avoid areas where dominant predators are abundant (Arias-Del Razo et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2012\u003c/span\u003e, Heithaus \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2005\u003c/span\u003e, Heithaus et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2007\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2008\u003c/span\u003e, Johnson et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2007\u003c/span\u003e, Wirsing et al. \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2007a\u003c/span\u003e,\u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003eb\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eGrey reef sharks and red bass had centres of activity around and within the reef channel and on the outer reef crest. Both species probably take advantage of the opportunity for energy saving offered by the currents, eddies and updrafts that the restriction and resulting acceleration of water flow creates as it passes through the channel. It has been estimated that updrafts induced by the current in channel systems and on reef slopes in French Polynesia can reduce energy expenditures of grey reef sharks by 10\u0026ndash;15%, (Papastamatiou et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Similar energy savings are likely to be available to other reef fishes such as red bass and may be one reason that channels and reef passes are habitats where many species of large reef fishes congregate during the day (Fisher et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Additionally, reef passages may also aggregate both plankton and the small planktivorous fishes that are likely to be the prey of these mesopredators, particularly on incoming tides (Fisher et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e, Papastamatiou et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eBecause of the opportunity for energy conservation and food acquisition, outer reef crest and channel entrance habitats are likely to be occupied by the largest, competitively dominant reef sharks (Papastamatiou et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Where these large individuals have been removed by fishing, as is the case at Scott Reefs, it may offer the opportunity for smaller, juvenile sharks to reside in these habitats. These smaller sharks would otherwise be competitively excluded or subject to predation by larger adults. This may explain why, at the Rowley Shoals, grey reef sharks occupied habitats across the lagoon and outer reef slope whereas at the Scott Reefs, where the largest adult sharks have been removed by fishing, the remaining juvenile grey reef sharks we tagged occurred on outer reef slopes and in the channel and were rarely detected in the lagoon. This absence of grey reef sharks from habitats occupied by red bass at Scott Reefs may also account for the shift in diet of this teleost mesopredator between these reef systems. Barley et al. (2017 a) found that on the Scott Reefs, the diet of red bass included a much greater proportion of pelagic prey such as fishes and squid than at the Rowley Shoals, where the diet had a much larger component of benthic invertebrates. Such differences in diet have the potential to create trophic cascades in coral reef ecosystems (Meekan et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eBoth red bass and grey reef sharks were more active in the evenings in both reef systems. Detections of grey reef sharks by receivers were similar throughout most times of the day and peaked in the early evening, whereas detections of red bass climbed steadily from the late afternoon to peak in the late evening in both reef systems. These patterns are consistent with the characterisation of these species as mostly nocturnal predators (Nagelkerken et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2000\u003c/span\u003e) and suggest that these species were not displaying temporal patterns of resource partitioning. The reef habitats used by grey reef sharks showed little change in both location and extent between night and day, although there was a small reduction in area of reef used by red bass at night. This reduction could reflect the greater activity of reef sharks at this time, and/or changes in the spatial distribution of prey.\u003c/p\u003e\u003cp\u003eAlthough the Scott Reefs and Rowley Shoals offer a unique natural experiment to compare the impact of reef sharks on mesopredator communities, as others have noted, such uncontrolled comparisons are open to a variety of alternative scenarios that might explain our results (Barley \u0026amp; Meeuwig \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). For example, differences in the spatial patterns of overlap between sharks and red bass might be due to changes in the distribution of some key resource (e.g. food, shelter) between these reef systems. We cannot exclude this possibility, although our results were consistent with \u003cem\u003ea priori\u003c/em\u003e predictions of what might occur if competition between these large mesopredators was an important driver of distribution patterns. Additionally, previous analysis with the same tacking dataset used here showed grey reef sharks display greater movement extent within an atoll (Clerke Reef) and across a reef system (Rowley Shoals or Scott Reefs) than red bass, but connectivity patterns differed between male and female sharks (Ferreira et al \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eOur sample size for red bass was also limited, which may have influenced the strength of some inferences made from our results. The configuration of acoustic arrays and occasional tag collisions may have further constrained the number of red bass that could be effectively monitored, as is common for species with small home ranges (Kessel et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). However, grey reef shark data from 2008 and 2015 deployments yielded consistent spatial patterns, suggesting robust characterisation of their movement and residency behaviour. Red bass exhibited more sporadic detections than sharks, perhaps due to their closer association with reef structure, which may interfere with tag transmissions. At the Rowley Shoals, there were regular monthly cycles in detections of red bass. Why these patterns occurred is not clear, but they may reflect cycles in the availability of prey in the water column or near the benthos, with ascent by the red bass to feed increasing the likelihood of tag transmissions being detected by the receiver stations, or alternatively, the presence of food within the reef matrix decreasing the likelihood of detection. Gaps in detections from March to June coincided with increased minimum convex polygon (MCP) areas, which may reflect seasonal spawning movements (Marriott et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2007\u003c/span\u003e, Wright et al. \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e1986\u003c/span\u003e). At the Scott Reefs, there was little predictability in the sporadic pattern of transmissions of tagged red bass.\u003c/p\u003e\u003cp\u003eAdditional data are needed to better understand the mechanisms of spatial partitioning and trophic dynamics of red bass and grey reef sharks. Analyses of movement in relation to tidal and lunar cycles could improve understanding of habitat use, particularly in dynamic channel environments (Laurioux et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The use of depth sensors and accelerometers would provide valuable insight into vertical movements, energetic expenditure, and habitat utilisation (Papastamatiou et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, Vianna et al. \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Stable isotope analysis of tissues collected during tagging could complement telemetry data and clarify dietary overlap and resource partitioning (Tilley et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Baited Remote Underwater Video (BRUV) systems could further elucidate behavioural interactions and risk effects between these mesopredators (Lester et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2020\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eResidency indices were high for many individuals of both species at both study locations supporting previous findings of strong site fidelity in reef-associated predators (Espinoza et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The restricted spatial extent of core activity areas suggests that both species may be effectively managed through appropriately designed marine protected areas (MPAs). These findings reinforce the importance of integrating ecological knowledge into spatial conservation planning for reef-associated predators.\u003c/p\u003e"},{"header":"5. CONCLUSION","content":"\u003cp\u003eOur study underscores the complex interactions between red bass and grey reef sharks at Scott Reefs and Rowley Shoals. On reefs with higher abundances of sharks, we observed some spatial partitioning in areas of core use by these species. This suggests that the presence of sharks influence the spatial behaviour of red bass, potentially as an adaptive strategy to reduce competitive pressures or predation risks. However, multiple mechanisms can support this coexistence. Given the variability in interactions we observed - from significant overlaps to possible spatial partitioning - it is clear that the organisation of space is not the only driving force allowing co-existence of these species. Other forms of resource partitioning, such as dietary differences (Barley et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003eb\u003c/span\u003e), could support the coexistence of these mesopredators in the same habitats, for instance through plasticity in diet driven by differing predation pressure or environmental conditions between reefs. This complexity, and the possible influence of human threats such as fishing on shark abundance and spatial dynamics highlight the need for further research and targeted conservation efforts that are sensitive to the fine-scale interdependencies and unique roles large mesopredators have within coral reef ecosystems.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eConflict of Interest\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\u003ch2\u003eEthics Approval\u003c/h2\u003e\u003cp\u003eThis research used existing acoustic telemetry data collected under animal ethics approvals reported in Field et al. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). No new animal handling occurred for this study.\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThis research was supported by the Australian Institute of Marine Science (AIMS) and the Integrated Marine Observing System (IMOS), and conducted as part of a Master\u0026rsquo;s research project within the International Master of Science in Marine Biological Resources (IMBRSea) programme.\u003c/p\u003e\u003ch2\u003eAuthors\u0026rsquo; Contribution\u003c/h2\u003e\u003cp\u003eAll authors meet authorship criteria, have approved the submitted version, and agree to publication. The work is original and not under consideration elsewhere.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThis study was supported by the Australian Institute of Marine Science and the Australian Integrated Marine Observing System (IMOS). Data were sourced from IMOS and is enabled by the National Collaborative Research Infrastructure Strategy (NCRIS). This work was part of the International Master of Science in Marine Biological Resources (IMBRSea) by LMD and was supported by the Oceans Institute at the University of Western Australia.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAcoustic tracking data from the Integrated Marine Observing System-Animal Tracking Facility is freely accessible through the AODN portal (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://portal.aodn.org.au/\u003c/span\u003e\u003cspan address=\"https://portal.aodn.org.au/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003e).\u003c/span\u003e The R code used in this study will be available upon request\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAppert C, Udyawer V, Simpfendorfer CA, Heupel MR, Scott M, Currey-Randall LM, Harborne AR, Jaine F, Chin A (2023) Use, misuse, and ambiguity of indices of residence in acoustic telemetry studies. Mar Ecol Prog Ser 714:27\u0026ndash;44\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eArias-Del Razo I, Hern\u0026aacute;ndez L, Laundr\u0026eacute; JW, Velasco-V\u0026aacute;zquez L (2012) The landscape of fear: habitat use by a predator (Canis latrans) and its main prey (\u003cem\u003eLepus californicus\u003c/em\u003e and \u003cem\u003eSylvilagus audubonii\u003c/em\u003e). Can J Zool 90:683\u0026ndash;693\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eArmstrong RA, McGehee R (1976) Coexistence of species competing for shared resources. Theor Popul Biol 9:317\u0026ndash;328\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarley SC, Clark TD, Meeuwig JJ (2020) Ecological redundancy between coral reef sharks and predatory teleosts. Rev Fish Biol Fish 30:153\u0026ndash;172\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarley SC, Meekan MG, Meeuwig JJ (2017a) Diet and condition of mesopredators on coral reefs in relation to shark abundance. PLoS ONE 12:e0165113\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarley SC, Meekan MG, Meeuwig JJ (2017b) Species diversity, abundance, biomass, size and trophic structure of fish on coral reefs in relation to shark abundance. Mar Ecol Prog Ser 565:163\u0026ndash;179\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarley SC, Meeuwig JJ (2017) The power and pitfalls of large-scale. unreplicated Nat experiments Ecosystems 20:331\u0026ndash;339\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBascompte J, Meli\u0026aacute;n CJ, Sala E (2005) Interaction strength combinations and the overfishing of a marine food web. Proc Natl Acad Sci USA 102:5443\u0026ndash;5447\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBradley D, Conklin E, Papastamatiou YP, McCauley DJ, Pollock K, Pollock A, Kendall BE, Gaines SD, Caselle JE (2017) Resetting predator baselines in coral reef ecosystems. Sci Rep 7:43131\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCalenge C (2023) Home range estimation in R: the adehabitatHR package. R package documentation\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChin A, Tobin A, Simpfendorfer C, Heupel M (2012) Reef sharks and inshore habitats: patterns of occurrence and implications for vulnerability. Mar Ecol Prog Ser 460:115\u0026ndash;125\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eD\u0026rsquo;Agata S, Vigliola L, Graham NAJ, Wantiez L, Parravicini V, Vill\u0026eacute;ger S, Mou-Tham G, Frolla P, Friedlander AM, Kulbicki M, Mouillot D (2016) Unexpected high vulnerability of functions in wilderness areas: evidence from coral reef fishes. Proc R Soc B 283:20160128\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEdgar G, Mellin C, Turak E, Stuart-Smith R, Cooper A, Ceccarelli D (2020) Reef Life Survey assessment of coral reef biodiversity in the North-west Marine Parks Network. Reef Life Survey Foundation Inc., Hobart\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEnvironment Australia (2002) Ashmore Reef National Nature Reserve and Cartier Island Marine Reserve management plans. Environment Australia, Canberra\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEspinoza M, Heupel MR, Tobin AJ, Simpfendorfer CA (2015) Residency patterns and movements of grey reef sharks (\u003cem\u003eCarcharhinus amblyrhynchos\u003c/em\u003e) in semi-isolated coral reef habitats. Mar Biol 162:343\u0026ndash;358\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFerreira LC, Galaiduk R, Radford B, Udyawer V, Meekan M, Thums M, Harcourt R, Lee KA, Treml EA (2025) Marine predator movements create seascape connectivity in remote coral-reef ecosystems. Mov Ecol 13:72\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eField IC, Meekan MG, Speed CW, White W, Bradshaw CJA (2011) Quantifying movement patterns for shark conservation at remote coral atolls in the Indian Ocean. Coral Reefs 30:61\u0026ndash;71\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFisher EE, Choat JH, McCormick MI, Cappo M (2018) Relative influence of environmental factors on the timing and occurrence of multi-species coral reef fish aggregations. PLoS ONE 13:e0209234\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFrisch AJ, Ireland M, Rizzari JR, L\u0026ouml;nnstedt OM, Magnenat KA, Mirbach CE, Hobbs JPA (2016) Reassessing the trophic role of reef sharks as apex predators on coral reefs. Coral Reefs 35:459\u0026ndash;472\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGause GF (1932) Experimental studies on the struggle for existence. J Exp Biol 9:389\u0026ndash;402\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGraham NAJ, Spalding MD, Sheppard CRC (2010) Reef shark declines in remote atolls highlight the need for multi-faceted conservation action. Aquat Conserv Mar Freshw Ecosyst 20:543\u0026ndash;548\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGrigg RW, Polovina JJ, Atkinson MJ (1984) Model of a coral reef ecosystem. Coral Reefs 3:23\u0026ndash;27\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuillemot N, Kulbicki M, Chabanet P, Vigliola L (2011) Functional redundancy patterns reveal non-random assembly rules in a species-rich marine assemblage. PLoS ONE 6:e26735\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHeithaus MR (2005) Habitat use and group size of pied cormorants (\u003cem\u003ePhalacrocorax varius\u003c/em\u003e) in a seagrass ecosystem: possible effects of food abundance and predation risk. Mar Biol 147:27\u0026ndash;35\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHeithaus MR, Frid A, Wirsing AJ, Dill LM, Fourqurean JW, Burkholder D, Thomson J, Bejder L (2007) State-dependent risk-taking by green sea turtles mediates top-down effects of tiger shark intimidation in a marine ecosystem. J Anim Ecol 76:837\u0026ndash;844\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHeithaus MR, Frid A, Wirsing AJ, Worm B (2008) Predicting ecological consequences of marine top predator declines. Trends Ecol Evol 23:202\u0026ndash;210\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHeupel MR, Semmens JM, Hobday AJ (2006) Automated acoustic tracking of aquatic animals: scales, design and deployment of listening station arrays. Mar Freshw Res 57:113\u0026ndash;122\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHoenner X, Huveneers C, Steckenreuter A, Simpfendorfer C, Tattersall K, Jaine F, Atkins N, Babcock R, Brodie S, Burgess J, Campbell H, Heupel M, Pasquer B, Proctor R, Taylor MD, Udyawer V, Harco R (2018) Australia\u0026rsquo;s continental-scale acoustic tracking database and its automated quality control process. Sci Data 5:180206\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHorne JS, Garton EO, Krone SM, Lewis JS (2007) Analyzing animal movements using Brownian bridges. \u003cem\u003eEcology\u003c/em\u003e88:2354\u0026ndash;2363\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHussey NE, Kessel ST, Aarestrup K, Cooke SJ, Cowley PD, Fisk AT, Harcourt RG, Holland KN, Iverson SJ, Kocik JF, Mills Flemming JE, Whoriskey FG (2015) Aquatic animal telemetry: a panoramic window into the underwater world. Science 348:1255642\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJohnson CN, Isaac JL, Fisher DO (2007) Rarity of a top predator triggers continent-wide collapse of mammal prey: dingoes and marsupials in Australia. Proc R Soc B 274:341\u0026ndash;346\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKessel ST, Cooke SJ, Heupel MR, Hussey NE, Simpfendorfer CA, Vagle S, Fisk AT (2014) A review of detection-range testing in aquatic passive acoustic telemetry studies. Rev Fish Biol Fish 24:199\u0026ndash;218\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKie JG (2013) A rule-based ad hoc method for selecting a bandwidth in kernel home-range analyses. Anim Biotelem 1:13\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKraft S, Gandra M, Lennox RJ, Mourier J, Winkler AC, Abecasis D (2023) Residency and space-use estimation methods based on passive acoustic telemetry data. Mov Ecol 11:2\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLaurioux A, Huveneers C, Papastamatiou Y, Planes S, Ballesta L, Mourier J (2024) Abiotic drivers of the space use and activity of gray reef sharks \u003cem\u003eCarcharhinus amblyrhynchos\u003c/em\u003e in a dynamic tidal environment. J Fish Biol 105:15\u0026ndash;30\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLester EK, Langlois TJ, Simpson SD, McCormick MI, Meekan MG (2020) The hemisphere of fear: the presence of sharks influences the three-dimensional behaviour of large mesopredators in a coral reef ecosystem. Oikos 129:1371\u0026ndash;1384\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLester EK, Langlois TJ, Simpson SD, McCormick MI, Meekan MG (2021) Reef-wide evidence that the presence of sharks modifies behaviours of teleost mesopredators. Ecosphere 12:e03301\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLester EK, Langlois T, Lindgren I, Birt M, Bond T, McLean D, Vaughan B, Holmes TH, Meekan MG (2022) Drivers of variation in occurrence, abundance and behaviour of sharks on coral reefs. Sci Rep 12:4024\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLucifora LO, Garc\u0026iacute;a VB, Worm B (2011) Global diversity hotspots and conservation priorities for sharks. PLoS ONE 6:e19356\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMacNeil MA, Chapman DD, Heupel M, Simpfendorfer CA, Heithaus M, Meekan M, Harvey E, Goetze J, Kiszka J, Bond ME, Currey-Randall LM, Speed CW, Sherman CS, Rees MJ, Udyawer V, Flowers KI, Clementi G, Valentin-Albanese J, Gorham T, Cinner JE (2020) Global status and conservation potential of reef sharks. Nature 583:801\u0026ndash;806\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMarriott RJ, Mapstone BD, Begg GA (2007) Age-specific demographic parameters and their implications for management of the red bass \u003cem\u003eLutjanus bohar\u003c/em\u003e (Forssk\u0026aring;l 1775): a large, long-lived reef fish. Fish Res 83:204\u0026ndash;215\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMeekan MG, Lester EK, Kron FJ, Barneche DR (2025) Predator removals, trophic cascades and outbreaks of crown-of-thorns starfish on coral reefs. Commun Biol 8:305\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMitchell JD, Schifiliti M, Birt MJ, Bond T, McLean DL, Barnes PB, Langlois TJ (2020) A novel experimental approach to investigate the potential for behavioural change in sharks in the context of depredation. J Exp Mar Biol Ecol 530\u0026ndash;531:151440\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMouillot D, Vill\u0026eacute;ger S, Parravicini V, Kulbicki M, Arias-Gonz\u0026aacute;lez JE, Bender M, Chabanet P, Floeter SR, Friedlander A, Vigliola L, Bellwood DR (2014) Functional over-redundancy and high functional vulnerability in global fish faunas on tropical reefs. Proc Natl Acad Sci USA 111:13757\u0026ndash;13762\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMourier J, Maynard J, Parravicini V, Ballesta L, Clua E, Domeier ML, Planes S (2016) Extreme inverted trophic pyramid of reef sharks supported by spawning groupers. Curr Biol 26:2011\u0026ndash;2016\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMunroe S, Huveneers C (2019) Monitoring the presence and residency of sharks at key locations off Victor Harbor (Encounter Marine Park). Report 2. Flinders University, Adelaide. (March 2016 \u0026ndash; October 2018\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNagelkerken I, Dorenbosch M, Verberk WCEP, Cocheret de la Morini\u0026egrave;re E, van der Velde G (2000) Day\u0026ndash;night shifts of fishes between shallow-water biotopes of a Caribbean bay, with emphasis on the nocturnal feeding of Haemulidae and Lutjanidae. Mar Ecol Prog Ser 194:55\u0026ndash;64\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePaine RT (1992) Food-web analysis through field measurement of per capita interaction strength. Nature 355:73\u0026ndash;75\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePapastamatiou YP, Huveneers C, Ballesta L, Planes S, Mourier J (2025) Marine predator super-habitats: channels used for foraging, resting, mating, and parturition in sharks. Biol Conserv 311:111446\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePapastamatiou YP, Iosilevskii G, Di Santo V, Huveneers C, Hattab T, Planes S, Ballesta L, Mourier J (2021) Sharks surf the slope: current updrafts reduce energy expenditure for aggregating marine predators. J Anim Ecol 90:2302\u0026ndash;2314\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePapastamatiou YP, Wetherbee BM, Lowe CG, Crow GL (2006) Distribution and diet of four species of carcharhinid shark in the Hawaiian Islands: evidence for resource partitioning and competitive exclusion. Mar Ecol Prog Ser 320:239\u0026ndash;251\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePimiento C, Albouy C, Silvestro D, Mouton TL, Velez L, Mouillot D, Judah AB, Griffin JN, Leprieur F (2023) Functional diversity of sharks and rays is highly vulnerable and supported by unique species and locations worldwide. Nat Commun 14:7691\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRizzari JR, Frisch AJ, Connolly SR (2014) How robust are estimates of coral-reef shark depletion? Biol Conserv 176:39\u0026ndash;47\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRobbins WD, Hisano M, Connolly SR, Choat JH (2006) Ongoing collapse of coral-reef shark populations. Curr Biol 16:2314\u0026ndash;2319\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRobbins WD, Renaud P (2016) Foraging mode of the grey reef shark \u003cem\u003eCarcharhinus amblyrhynchos\u003c/em\u003e under two different scenarios. Coral Reefs 35:253\u0026ndash;260\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRoff G, Doropoulos C, Rogers A, Bozec YM, Krueck NC, Aurellado E, Priest M, Birrell C, Mumby PJ (2016) The ecological role of sharks on coral reefs. Trends Ecol Evol 31:395\u0026ndash;407\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRoss ST (1986) Resource partitioning in fish assemblages: a review of field studies. \u003cem\u003eCopeia\u003c/em\u003e 1986:352\u0026ndash;388\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRuppert JLW, Travers MJ, Smith LL, Fortin MJ, Meekan MG (2013) Caught in the middle: combined impacts of shark removal and coral loss on the fish communities of coral reefs. PLoS ONE 8:e74648\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSalini J, Blaber S, Brewer D (1992) Diets of sharks from estuaries and adjacent waters of the north-eastern Gulf of Carpentaria, Australia. Mar Freshw Res 43:87\u0026ndash;96\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSherman CS, Simpfendorfer CA, Pacoureau N, Matsushiba JH, Yan HF, Walls RHL, Rigby CL, VanderWright WJ, Jabado RW, Pollom RA, Carlson JK, Charvet P, Bin Ali A, Fahmi, Cheok J, Derrick DH, Herman KB, Finucci B, Eddy TD, Palomares MLD, Avalos-Castillo CG, Kinattumkara B, Blanco-Parra MP, Dharmadi, Espinoza M, Fernando D, Haque AB, Mej\u0026iacute;a-Falla PA, Navia AF, P\u0026eacute;rez-Jim\u0026eacute;nez JC, Utzurrum J, Yuneni RR, Dulvy NK (2023) Half a century of rising extinction risk of coral-reef sharks and rays. Nat Commun 14:15\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSimpfendorfer CA, Heupel MR, Hueter RE (2002) Estimation of short-term centres of activity from an array of omnidirectional hydrophones and its use in studying animal movements. Can J Fish Aquat Sci 59:23\u0026ndash;32\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSpeed CW, Meekan MG, Field IC, McMahon CR, Stevens JD, McGregor F, Huveneers C, Berger Y, Bradshaw CJA (2011) Spatial and temporal movement patterns of a multi-species coastal reef shark aggregation. Mar Ecol Prog Ser 429:261\u0026ndash;275\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSpeed CW, Meekan MG, Field IC, McMahon CR, Abrantes K, Bradshaw CJA (2012) Trophic ecology of reef sharks determined using stable isotopes and telemetry. Coral Reefs 31:357\u0026ndash;367\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSpeed CW, Meekan MG, Field IC, McMahon CR, Stevens JD, McGregor F, Huveneers C, Berger Y, Bradshaw CJA (2011) Spatial and temporal movement patterns of a multi-species coastal reef shark aggregation. Mar Ecol Prog Ser 429:261\u0026ndash;275\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSpeed CW, Rees MJ, Cure K, Vaughan B, Meekan MG (2019) Protection from illegal fishing and shark recovery restructures mesopredatory fish communities on a coral reef. Ecol Evol 9:10553\u0026ndash;10566\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTilley A, L\u0026oacute;pez-Angarita J, Turner JR (2013) Diet reconstruction and resource partitioning of a Caribbean marine mesopredator using stable-isotope Bayesian modelling. PLoS ONE 8:e79560\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTruchy A, G\u0026ouml;the E, Angeler DG, Ecke F, Sponseller RA, Bundschuh M, Johnson RK, McKie BG (2019) Partitioning spatial, environmental and community drivers of ecosystem functioning. Landsc Ecol 34:2371\u0026ndash;2384\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eUdyawer V, Dwyer RG, Hoenner X, Babcock RC, Brodie S, Campbell HA, Harcourt RG, Huveneers C, Jaine FRA, Simpfendorfer CA, Taylor MD, Heupel MR (2018) A standardised framework for analysing animal detections from automated tracking arrays. Anim Biotelem 6:17\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003evan Zinnicq Bergmann MPM, Griffin LP, Bodey TW, Guttridge TL, Aarts G, Heithaus MR, Smukall MJ, Papastamatiou YP (2024) Intraguild processes drive space-use patterns in a large-bodied marine predator community. J Anim Ecol 93:876\u0026ndash;890\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVianna GMS, Meekan MG, Meeuwig JJ, Speed CW (2013) Environmental influences on patterns of vertical movement and site fidelity of grey reef sharks (\u003cem\u003eCarcharhinus amblyrhynchos\u003c/em\u003e) at aggregation sites. PLoS ONE 8:e60331\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWatsky MA, Gruber SH (1990) Induction and duration of tonic immobility in the lemon shark \u003cem\u003eNegaprion brevirostris\u003c/em\u003e. Fish Physiol Biochem 8:207\u0026ndash;210\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWilliams LH, Anstett A, Bach Mu\u0026ntilde;oz V, Chisholm J, Fallows C, Green JR, Higuera-Rivas JE, Skomal G, Winton M, Hammerschlag N (2021) Sharks as exfoliators: widespread chafing between marine organisms suggests an unexplored ecological role. Ecology 102:e03570\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWilliamson MJ, Tebbs EJ, Dawson TP, Jacoby DMP (2019) Satellite remote sensing in shark and ray ecology, conservation and management. Front Mar Sci 6:135\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWilson BR (2013) The biogeography of the Australian North West Shelf: environmental change and life\u0026rsquo;s response. \u003cem\u003eGeological Society of London, Memoir 38\u003c/em\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWirsing AJ, Heithaus MR, Dill LM (2007a) Can you dig it? Use of excavation, a risky foraging tactic, by dugongs is sensitive to predation danger. Anim Behav 74:1085\u0026ndash;1091\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWirsing AJ, Heithaus MR, Dill LM (2007b) Fear factor: do dugongs (\u003cem\u003eDugong dugon\u003c/em\u003e) trade food for safety from tiger sharks (\u003cem\u003eGaleocerdo cuvier\u003c/em\u003e)? Oecologia 153:1031\u0026ndash;1040\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWright A, Dalzell PJ, Richards AH (1986) Some aspects of the biology of the red bass \u003cem\u003eLutjanus bohar\u003c/em\u003e (Forssk\u0026aring;l) from the Tigak Islands, Papua New Guinea. J Fish Biol 28:533\u0026ndash;544\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"marine-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mabi","sideBox":"Learn more about [Marine Biology](https://www.springer.com/journal/227)","snPcode":"227","submissionUrl":"https://submission.nature.com/new-submission/227/3","title":"Marine Biology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"acoustic telemetry, coral reef, competition, fishing pressure, Indo-Pacific, KUD, shark ecology, spatial partitioning","lastPublishedDoi":"10.21203/rs.3.rs-8209051/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8209051/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCoral reefs host high densities of large mesopredators occupying upper trophic levels. Understanding how these species partition space is essential to reveal underlying ecological dynamics and inform conservation. We hypothesised that red bass (\u003cem\u003eLutjanus bohar\u003c/em\u003e) and grey reef sharks (\u003cem\u003eCarcharhinus amblyrhynchos\u003c/em\u003e) exhibit spatial and/or temporal partitioning influenced by species-specific behaviour and historical fishing pressure. To test this, we used acoustic telemetry to investigate habitat partitioning between these two large mesopredators at the Rowley Shoals and the Scott Reefs, Western Australia. These analyses were based on acoustic detections collected between 2007 and 2016 at the Rowley Shoals (17\u0026deg;20\u0026rsquo;S, 119\u0026deg;10\u0026rsquo;E) and the Scott Reefs (14\u0026deg;3\u0026rsquo;S, 121\u0026deg;46\u0026rsquo;E) on the north-western Australian continental shelf. Analysis of 95% kernel utilisation distributions (KUDs) showed broad spatial overlap, with both species frequently occupying habitats near reef fronts and channels. However, 50% KUDs revealed finer-scale partitioning: at the Rowley Shoals, core space use overlapped by less than 20%, whereas at the Scott Reefs, overlap exceeded 60%. These differences likely reflect historical fishing pressure, particularly the depletion of adult reef sharks at the Scott Reefs. There was little evidence of temporal partitioning. Both species were most active in the evening and highly resident in the same habitats throughout the year. Red bass exhibited wider-ranging movements from March to June, likely associated with spawning activity while grey reef sharks exhibited consistent presence and high site fidelity year-round. These findings underscore the influence of mesopredator size structure and abundance on spatial behaviour and highlight the conservation value of no-take marine reserves.\u003c/p\u003e","manuscriptTitle":"Effects of Shark Removal on Spatial Partitioning Among Large Mesopredators on Coral Reefs","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-04 05:52:41","doi":"10.21203/rs.3.rs-8209051/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-12-05T18:23:51+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-02T16:37:04+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-27T11:52:57+00:00","index":"","fulltext":""},{"type":"submitted","content":"Marine Biology","date":"2025-11-26T01:01:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"marine-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mabi","sideBox":"Learn more about [Marine Biology](https://www.springer.com/journal/227)","snPcode":"227","submissionUrl":"https://submission.nature.com/new-submission/227/3","title":"Marine Biology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"9739d68e-0071-466b-99a2-1524b1d0be8f","owner":[],"postedDate":"December 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-12-04T05:52:41+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-04 05:52:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8209051","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8209051","identity":"rs-8209051","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}