Behavioural patterns of Octopus tetricus (Mollusca: Cephalopoda) and their responses to fisheries trap and bait combinations

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However, given their complex behavioural repertoires, cognitive capacities and individual personalities among octopuses, careful consideration of their interactions with and capture by fishing gears is required to inform efficient, sustainable, and ethical fisheries development. Here, the behaviour of Octopus tetricus was assessed in response to different bait and trap combinations in an outdoor mesocosm experiment. Eight wild octopuses were collected, maintained in individual tanks with flow-through seawater and aeration, and monitored with a 24-h video surveillance system. Six different trap types and four different baits were presented to each octopus in various combinations during four sequential trials. Fine-mesh crab traps were the most successful in capturing octopus, accounting for 23 of the total 30 captures across all trials. Whereas solid trigger traps produced the greatest number of other interactions (e.g., octopus sitting on trap or in the entrance), averaging 43 interactions per trial, but were rarely triggered. Bait type did not influence octopus capture, trap interaction frequency, or octopus activity. Octopus were generally inactive, dedicating only 9.5% of their total time to active behaviours. Octopus activity varied with time of day, with peak activity during morning daylight (0800–1200) and the lowest activity during the dark hours of the very early morning (0000–0400). Additionally, capture numbers, trap interactions, and activity varied among individuals, with bolder personalities in some octopus. This natural variation among individual octopuses may lead to fishery-induced selection associated with the elevated capture frequency of bold or more active individuals. Octopus fisheries animal behaviour octopus ethics octopus activity Octopus tetricus Figures Figure 1 Figure 2 Figure 3 Introduction Cephalopods have become an increasingly valuable commodity, with interest growing in their use as a sustainable food source and as an important future food supply under climate change (Willer et al. 2023 ). During the last 50 years, there has been a 416% increase in cephalopod wild-caught fisheries landings, which reached a peak of 4 million tonnes in 2013 (Ospina-Alvarez et al. 2022 ). While many traditional finfish stocks are either fully fished or in decline (FAO 2020 ), cephalopod populations are generally thought to be increasing either in response to climate change or a reduced abundance of predators or a combination of these or similar factors (Doubleday et al. 2016 ). Nonetheless, the overexploitation of cephalopod species has occurred in some parts of the world and developing fisheries require appropriate management to ensure sustainability (Ospina-Alvarez et al. 2022 ). Furthermore, as evidence for potential sentience and the capacity to feel pain among cephalopods accumulates, which is particularly the case for octopuses, there has been increased scrutiny regarding animal welfare with respect to capture and culture methods (Mather and Anderson 2007 ; King and Marino 2019 ). Octopuses exhibit behavioural flexibility and many attributes suggestive of high intelligence. Although these attributes alone are insufficient evidence of complex cognition (Emery and Clayton 2004 ; Amodio 2019 ), they are considered precursors for many associated capacities, such as causal reasoning, imagination, and mental attribution (Schnell et al. 2021 ). Octopuses also exhibit introspection, a cognitive process used to evaluate consciousness (Mather and Andrade 2023 ); this process involves internally evaluating sensory input and making decisions before taking action. Furthermore, as Mather and Anderson ( 2007 ) and Mather ( 2019 ) suggest, octopuses can feel pain and display adverse behaviour in response to stress. The stress response systems in octopuses and vertebrates are neuronally and endocrinologically similar (Stefano et al. 2002 ), with octopuses showing consistent behavioural responses to pain in humans (Mather and Anderson 2007 ). Therefore, it is important to recognise the need to adopt a more robust ethical approach when dealing with such cognitively advanced invertebrates (King and Marino 2019 ), especially regarding fishing and culture methods that could induce either pain or stress. Other octopus behavioural attributes of direct relevance to fisheries biology are daily activity patterns and personality types. While traditionally thought to be mostly nocturnal, the activity patterns of octopuses are quite varied (Meisel et al. 2013 ); with contrasting daily activity patterns now documented for closely related species (Meisel et al. 2006 ), among species inhabiting the same area (Houck 1982 ), and within species (Kayes 1973 ; Mather 1988 ; Meisel et al. 2006 ). The presence of individual personality has also been described in octopuses. Three aspects of octopus temperament (activity, reactivity, and avoidance) show remarkable resemblance to those described for vertebrates (Mather and Anderson 1993 ). Furthermore, individual octopus behavioural tendencies can change over time, possibly due to lived experience and learning (Sinn et al. 2001 ; Sinn and Moltschaniwskyj 2005 ), and octopus behavioural traits can be inherited (Sinn et al. 2001 ). There is, therefore, scope for static fishing gears, like traps, to alter the personality frequencies within exploited populations through fishing-induced evolution driven by the differential removal of bold or active individuals (Uusi-Heikkilä et al. 2008). Fisheries targeting species of octopus using selective gears, which produce little or no bycatch or discards, are generally considered more sustainable, economical, and environmentally friendly than those deploying non-selective gears (Petetta et al. 2021 ). Enclosed static gears (like soaked pots and traps) tend to exhibit higher species- and size-selectivity of entrapment than active towed gears (like bottom trawls) or exposed static nets (like trammel nets, gill nets, fixed nets, and bottom set nets). Pots and traps also tend to have high survival rates for the bycatch that is incidentally caught (Kopp et al. 2020 ). Conversely, actively towed gears and exposed static nets used in mixed-species fisheries produce significant bycatch. These fisheries pose a threat to large marine vertebrates (Ferretti et al. 2008 ; Casale 2011 ), mammals (Bearzi 2002 ) and fish (Monteiro et al. 2001 ), who are entangled and captured as bycatch. Non-selective fishing gears exhibit significantly high discard rates with bottom-trawl fisheries responsible for the bulk of discards globally (Zeller et al. 2018 ). Alternatively, marine animals captured in pot and trap fishing gear are often alive and uninjured upon retrieval, so if undersized can be released alive, and if legal can demand a higher market price (Kopp et al. 2020 ). Hence, selective fishing methods for octopus are more ethical to the target species and more economical for individual fishers. In Australia, octopuses have been taken as bycatch in multi-species trawl fisheries and more recently have become a target species. Targeted trapping for octopus first started in 2001 with the development of the Western Australian Octopus Interim Managed Fishery (WAOIMF; Hart et al. 2016 ). This fishery targets Octopus djinda (previously known as Octopus cf. tetricus ; Amor and Hart 2021 ) and developed an active trigger trap (with a snap closing entrance door), which produced a ~ 400% increase in octopus catch (from 33 t in 2009 to 170 t in 2010) compared to the previously used shelter pots (Hart et al. 2016 ). The success of the WAOIMF sparked exploration of similar opportunities for the Eastern Australian octopus species Octopus tetricus in New South Wales (NSW). Octopus tetricus is a medium-sized, robust species with an arm span reaching up to 2 m (Hall and Moltschaniwskyj in press). It mainly inhabits rocky reefs, shallow seagrass beds, and sediment substrates (Anderson 1997 ), and utilises dens for refuge from predation (Anderson 1997 ), mating (Godfrey-Smith and Lawrence 2012 ; Caldwell et al. 2015 ), and egg rearing (Garci 2016). Octopus tetricus completes its life cycle within one to two years (Ramos et al. 2014 ) and employs a semelparous reproductive strategy (Anderson et al. 2002 ). The rapid growth and relatively short life span of O. tetricus potentially makes it an appropriate target species (Kelaher et al. 2018 ). However, there is currently insufficient biological and fisheries knowledge of O. tetricus to determine whether current catch levels are sustainable and whether further targeted fishing is feasible. In addition, it is not known whether common shelter pots that allow octopus to enter and leave (for feeding) are effective for catching O. tetricus or whether the WA trigger traps developed for O. djinda are appropriate to catch the smaller O. tetricus . Furthermore, the species’ activity patterns are likely to influence trapping catch rates and appropriate soak times, and these require further clarification in O. tetricus . To address this, we (1) investigated the behavioural response of O. tetricus to different combinations of trap designs and lures/baits; (2) designed and tested a novel ethical octopus trap; and (3) investigated the daily activity patterns of O. tetricus . Methods Collection, transportation, and acclimation of octopus Eight O. tetricus were captured within research survey crab traps at Lake Macquarie, NSW (-33.0311, 151.5603) and by hand at Sawtell, NSW (-30.376607, 153.101589). Each octopus was transported to the National Marine Science Centre (NSMC, Coffs Harbour, Australia − 30.2677 S, 153.1374 E) inside an individual 20-L bucket with mesh windows for water exchange that were placed into two 340-L insulated transporters at a stocking density of up to four octopuses each. The transporters were filled on-site with fresh seawater and kept aerated via a supply of diffuse pure oxygen. At the NMSC, the octopuses were transferred inside the buckets into 68-L plastic bins for acclimation to the mesocosm water over 3 h via gradual water transfer. The octopuses were provided a minimum seven-day settlement period to recover from transportation stress and acclimate to their new tank environment. There were no mortalities or obvious injuries during capture, transport, and acclimatisation to the mesocosms. Mesocosms and experimental setup Each octopus was individually housed in a 3000-L mesocosm comprising a fibreglass tank (2200 mm diameter × 800 mm height) furnished with a central habitat of pebble substrate, two artificial dens (terracotta pots), artificial plants and empty oyster shells. The tanks were located outdoors under a solid awning to protect against direct sunlight and rain. Each tank was supplied with flow-through ambient seawater pumped directly from the adjacent ocean at ambient temperature (ranging from 16.1–23.0 ℃, May to August 2022). Each mesocosm was monitored via a 24-h video surveillance system (Reolink: RLK16-810B8-A) with a 6 TB internal hard drive which was backed up daily. To ensure octopuses were visible at night, two infrared floodlights (Infront Technologies: IFT-IR80-96) were installed to the rim of each tank. It should be noted that octopuses exhibited no pupillary response to infrared light during a study conducted by Soto et al. ( 2020 ), suggesting octopuses are not able to see infrared light. After acclimation, each octopus was anaesthetised by immersion in a bath of magnesium chloride of 3.25% concentration (MgCl, 32.5 g. L − 1 ). The dosage was increased from the recommended 2.70% concentration (27 g. L-1, as recommended by the Department of Primary Industries 2015) due to insufficient anaesthesia after ~ 13 minutes of submersion. On average, octopuses required 15 minutes of submersion in the stronger MgCl solution to be sufficiently sedated. Once anaesthetised, each octopus was weighed, and its dorsal mantle length (DML) was measured. Each octopus was then injected in the base of the third left arm with a fluorescent dye (oxytetracycline, OTC, 50 mg. L − 1 solution administered at 100 mg. Kg − 1 body weight), to mark internal hard structures and a passive integrated transponder (PIT) microchip tag (weighing 0.01 g, at 2 × 11 mm) was inserted via a hypodermic needle into the subcutaneous tissue between the first and second left arm of the octopus. These latter procedures were completed for a related study, with the results reported elsewhere. The octopuses were then submerged in a fresh seawater bath with an aerator for recovery before return to mesocosms. Experimental trials Experiments to test hypotheses about trap and bait effectiveness began in July 2022. Twenty-four-hour video footage of the octopuses (n = 8) was collected for three days under normal mesocosm conditions before traps were introduced. This provided a baseline for behaviours and activity levels of each octopus that might influence their response during the subsequent trap and bait trials. Twenty-four-hour video footage was then collected for the duration of each of the following trap and bait trials. An initial trap trial was completed over seven days (168 h) to assess each octopuses’ behavioural responses to five different trap types that were introduced on the first day: (1) solid trigger trap; (2) fine-mesh crab trap; (3) novel oyster trap; (4) single-entrance PVC pipe; and (5) double-entrance PVC pipe (Table 1 , Figure S1). One of each of these five traps were placed in each tank with the trap entrances equidistant from the central habitat to avoid proximity bias. All were baited with a plain artificial orange plastic crab lure (Table 2 , Figure S2). If an octopus was caught it was released at feeding times (between 0900–1000) each day. If an octopus was captured again during that day, they were left until the next day to assess the trap’s capacity to prevent escape. The trigger trap was excluded from this condition, given that escape was not possible from this trap type and did not allow water exchange into the trap once it was triggered. Therefore, octopuses were released from trigger traps as soon as possible after capture. Upon conclusion of the trial, all traps were removed, and the octopuses were given a 5-day recovery period. Table 1 Description of the trap types used in the experiment Trap Type Description Trigger trap WA solid plastic trigger trap. Dimensions: \(620 \text{m}\text{m}\times 220 \text{m}\text{m}\times 280 \text{m}\text{m} (\text{L}\times \text{W}\times \text{H})\) . Crab trap Custom fine-mesh, round crab trap with three funnel entrances. Dimensions: \(700 \text{m}\text{m} {\varnothing}, 18 \text{m}\text{m} \text{m}\text{e}\text{s}\text{h}\) . Oyster trap Custom mesh shelter pot. Dimensions: \(460 \text{m}\text{m}\times 230 \text{m}\text{m} {\varnothing}; 5 \text{m}\text{m} \text{m}\text{e}\text{s}\text{h}\) . Single-entrance shelter pot Custom single-entrance shelter pot. Polyvinyl chloride (PVC) pipe. Dimensions: \(500 \text{m}\text{m}\times 100 \text{m}\text{m} {\varnothing}\) . Double-entrance shelter pot Custom double entrance shelter pot. PVC straight pipe \(300 \text{m}\text{m}\times 100 \text{m}\text{m} {\varnothing}\) with a PVC \(45^\circ\) junction \(100 \text{m}\text{m} {\varnothing}\) . Overall length: \(520 \text{m}\text{m}\) . Hybrid trap Novel trap design: a combination of the (1) trigger and (2) crab traps. A cylinder-shaped mesh trap with a shelter pot base and crab trap entrance. Dimensions: 590 \(\text{m}\text{m}\times 240 \text{m}\text{m} {\varnothing}; 5 \text{m}\text{m} \text{m}\text{e}\text{s}\text{h}\) . Table 2 Description of the lure/bait types used in the experiment Bait type Description Plain A clean, plain silicone crab lure. Light Silicone crab lure with an LED light attached. Tuna oil A silicone crab lure smothered in Tuna oil (store-bought from a fishing and tackle shop). Tuna bait pellet A silicone crab lure with a tune bait pellet stuffed inside the lure. The bait trials consisted of three consecutive trials lasting 72 h each with at least 24 h recovery period between trials. During each trial, the octopuses’ behavioural responses to a single, randomly assigned trap type with different lure/bait type combinations were assessed. This was achieved by placing four of the same trap type in each tank, with each trap containing a different lure/bait type. Results from the first trap trial informed the decision to include only the most successful traps (i.e., trigger-, crab-, and a novel hybrid trap) in the bait trials (Table 1 ). The novel hybrid trap was designed to include design elements that appealed to the hunting and sheltering instincts of octopus. The four bait types used in the experiment included: (1) a plain artificial orange plastic crab lure; (2) crab with LED light; (3) crab with tuna oil; and (4) crab with tuna bait-pellet (Table 2 , Figure S2). The crab with LED light is the current bait type used in the WA OIMF and is being trialled in the NSW developmental octopus fishery. The tuna oil (3) and tuna bait pellet (4) treatments were suggested by commercial fishers as possible enhancements to improve catch rates in commercial fishing. The placement of lure/bait types within the tank was randomised to avoid learning or proximity bias. At the end of the experiment, each octopus was euthanized in a bath of 7.5% MgCl and dissected to remove all hard structures (statoliths, stylets and beaks) and a tissue sample for later ageing and genetic analysis (reported elsewhere) and record other biological information, such as sex and reproductive stage. Behavioural analyses For each of the three experiments, a time budget and frequency counts of specific behaviours of interest (see SI Table S1) were used to quantify the activity patterns of each octopus and their responses to the trap and lure/bait types. A total of 18 behaviours were considered (see SI Table S1) based on pre-experiment observations of the octopuses and previous studies and ethograms of the same or similar octopus species (Mather and Alupay 2016 ; Dominguez-Lopez et al. 2021 ). Behaviours were grouped into four main categories: den-associated-, other-active-, trap-associated- and other behaviours. At the end of each trial, all video footage of the octopuses was examined using 2-minute interval focal sampling. This involved observing and recording the behaviour of each individual octopus every 2 minutes for the entirety of the experiment. This produced 93,044 total observation data points. Data analyses All data analyses were performed using R version 4.2.2 (R Core Team 2022). Generalised Linear Mixed Models (GLMMs) from the ‘lme4’ package (Bates 2010 ) were used to test hypotheses about the influence of different combinations of fixed and random explanatory variables on: (a) the number of octopus captures; (b) the behavioural responses (number of interactions) of O. tetricus with different trap and bait combinations; and (c) the daily activity patterns of O. tetricus . This was achieved by fitting a random-effects base-model, followed by forward selection of fixed factors and relevant interaction terms. Model fits were compared using likelihood ratio tests (chi-squared goodness of fit and corresponding p-value) and Akaike Information Criteria (AICs) for each combination of models. The explanatory power of the random effects was assessed using the level of variation ( var. ) explained in the base model. As bait was not found to explain significant variation in any trials, data from the two trap trials were pooled to increase the power for testing the significant influence of other effects. Finally, post-hoc Tukey’s pairwise comparisons were used to: (a) test for differences in number of captures among trap types; (b) determine the influence of trap types on the number of interactions; (c) test for differences in activity levels during different times of the day (Time Periods, see below). The octopus capture data were analysed using binomial logistic regression models, with capture or not as the binomial response variable and a logit link function. Trap type and bait type were included as fixed effects, and tank number (i.e., individual octopuses with varying personalities) and day number (nested within trial number) were included as random effects. The octopuses’ trap-associated behaviours (see SI Table S1) were analysed to determine the frequency of octopus interactions with different trap and bait combinations. For these analyses, the response variable was the frequency (count) of 2-min intervals that included interactive behaviours and, like most categorical behavioural data, included a high proportion of zeros. Therefore, negative binomial models with a logit link were fit to these count data, due to overdispersion with the Poisson distribution. Trap-type and bait-type were included as fixed factors and tank number, and day number (nested within trial number) were included as random effects. For the activity pattern analyses, only active behaviours were analysed, which included other-active and trap-associated active behaviours (see SI Table S1), and total combined activity and excluded den-associated behaviours. These count data were also fitted with negative binomial models with a log link function, because of overdispersion with the Poisson distribution. These activity data were analysed for the influence of a fixed factor ‘time period’, created by dividing each day into six time intervals: very early morning (0000–0400), dawn (0400–0800), morning (0800–1200), afternoon (1200–1600), dusk (1600–2000), and night (2000–2400). Random effects included tank number and day number (nested within trial number). Results Octopus capture A total of 30 captures occurred across all four trials, with two octopuses accounting for most of the captures (i.e., one octopus was captured 15 times, and another octopus was captured 9 times). Of the remaining six octopuses: two were caught twice, two were caught once and two were not caught at all. Trap type had a significant influence on the number of captures in all trials (GLMM; trap trial: χ 2 = 7.56, df = 1, p = 0.0059; bait trials: χ 2 = 13.15, df = 2, p = 0.0013; combined trials: χ 2 = 32.05, df = 3, p < 0.0001). The crab trap accounted for the largest number of octopus captures (23) across all trials, with a 10% probability of capturing an octopus (Table 3 ). The crab trap was more successful than the hybrid (Tukey’s; p = 0.0379) and trigger ( p = 0.0012) traps, which captured one and two octopus respectively, with a 1% probability of capture for each of these two trap types (Table 3 ). The oyster trap captured four octopuses in total, however, 100% of caught octopuses escaped within 2 minutes of capture, given that it had a permanent opening. One of the octopus caught in the trigger trap had an arm severed in the closing mechanism and subsequently died. Octopuses caught during the bait trial were spread evenly among the bait types, with no significant influence of bait type on octopus capture (GLMM; p = 0.84). Table 3 Number of captures for each trap type, including capture and escape probabilities Capture Trap Type Trigger trap Crab trap Oyster trap Hybrid trap No (0) 244 223 50 191 Yes (1) 2 23 4 1 Capture Probability 1% 10% 8% 1% No. of escapes 0 0 4 0 Escape probability 0% 0% 100% 0% Behavioural interactions The greatest frequency of interactions among octopuses and traps were recorded for those captured within a crab trap (Fig. 1 ). However, during those periods the octopuses were prevented from interacting with any other trap or bait types or interacting with the crab trap using a different behavioural response. Therefore, these interactions were excluded from further data analyses, which left, a total of 3,862 interactions across the four trials. Two octopus were responsible for ~ 60% of the remaining interactions (i.e., one octopus underwent 1,596 interactions and another octopus made 760 interactions), which resulted in significant variation among individuals (tank number) and days in the number of octopus interactions with traps during the first trap trial (GLMM random-effects model; tank number: var. = 1.11, day number: var. = 0.63; p = 0.0019). The frequency of octopus interactions with traps also depended significantly on trap type (GLMM; χ 2 = 64.81, df = 4, p < 0.0001), with significantly more interactions with trigger traps than any other trap type once captures in crab traps were removed (Tukey’s; p < 0.0001; Fig. 1 ), with an average of 43 interactions per observation combination. For the bait trial, there was no significant effect of trap nor bait type on the number of interactions (GLMM; trap type: p = 0.0869; bait type: p = 0.4716). There was also no significant variation among tanks nor days once captures in crab traps were removed (GLMM random-effects model: p = 0.31). Activity patterns Octopus activity levels ranged from ~ 4% to ~ 30%, with the rest of the time spent in their dens. On average, octopuses spent 9.5% of their time active. Activity patterns of octopuses differed significantly among individuals (tank number) and days within trials, but not among trials (GLMM random-effects model; tank number: var. = 0.4344; day number | trial number: var. = 0.1347; trial number: var. < 0.0001; p < 0.0001). Octopuses spent the largest proportion of their time active during the second day (10.7%) of the pre-trial, and the final day (23.3%) of the trap trial and were the least active on the second day (4.1%) of the trap trial. An octopuses’ total combined activity was significantly influenced by time of day (GLMM; χ 2 = 29.272, df = 29.27, p < 0.0001; Fig. 2 ). The highest level of activity occurred in the morning daylight (0800–1200) and at dusk (1600–2000); spending ~ 14% and ~ 11% of their time being active during these time periods, respectively. Octopuses were mostly inactive during the dark hours of the very early morning (0000–0400), with only ~ 6% of their time spent being active. They were significantly more active during morning daylight, from 0800–1200, than during the dark hours of the very early morning, from 0000–0400 (Tukey's; p < 0.0001), dawn, from 0400–0800 ( p = 0.0177) and during the afternoon, from 1200–1600 ( p = 0.0460). During the bait trials, an octopuses’ trap-associated activity was also significantly influenced by time of day (GLMM; χ 2 = 25.805, df = 5, p < 0.0001; Fig. 3 ), whereas other-activity was not ( p = 0.3377). Octopuses interacted with traps mostly in daylight, from 0800–1600 (morning and afternoon; 5.5%), and the least interactions occurred while it was dark, from 0000–0400 (very early morning; 1%), and during dawn, from 0400–0800 (1%). An octopuses’ trap-associated activity was significantly higher in the morning daylight from 0800–1200 than in the dark hours of the very early morning from 0000–0400 (Tukey's; p < 0.0001) and dawn from 0400–0800 ( p = 0.0035). Trap-associated activity was significantly lower in the dark hours of the very early morning (0000–0400) than in daylight (0800–1600; p = 0.0186) and during dusk (1600–2000; p = 0.0060). Discussion The 24 h surveillance of O. tetricus allowed us to observe and analyse their activity patterns and behavioural responses to proposed fishing gear. We found fine-mesh crab traps to be the most successful at octopus capture, while the solid trigger traps were the most attractive to octopus exploration. Contrary to expectation, the capture rates, behavioural interactions with traps and the activity patterns of octopuses were not significantly influenced by bait type. In general, octopuses were mostly sedentary and stayed within or near their established dens (terracotta pots). When they were active, octopuses demonstrated diurnal activity, peaking in the morning daylight (0800–1200), with the lowest activity during the dark hours of the very early morning (0000-0400). Octopus capture The success of the crab trap in capturing O. tetricus may be due to the methods employed by octopuses to explore novel objects. Octopuses typically use visual and tactile exploration to investigate novel objects, but only tactile assessment of known objects (Ovalle et al. 2023 ). Of the three trap types, the fine mesh of the crab traps allowed for the greatest visual exploration of the artificial lure from all angles and any distance. Octopuses can change their hunting strategies to adapt to their current environment and have been shown to be visual opportunists (Leite et al. 2009 ). Therefore, the transparent nature of the crab traps may spark opportunistic visual attacks by octopuses on a highly visible lure. Octopus are a well-known bycatch species in static gears that utilise a mesh structure such as the barrel-shaped lobster pots used in the South African Spiney Lobster fishery (Groeneveld et al. 2006 ) and the beehive pots employed by the South Australian Southern Rock Lobster fishery (Brock and Ward 2004 ). Although the most successful at capture, crab traps can pose significant problems when deployed in the wild. Crab traps deployed with natural baits are known for high bycatch rates and can cause mortality of dolphins (Tursiops truncates; Burdett and McFee 2023 ), seals (Kovacs et al. 2012 ) and turtles (Dorcas et al. 2007 ). Artificial lures may present a solution; during our trap trial, the crab traps were effective at capturing octopus with a plain bright orange crab artificial lure, which presented only visual and no olfactory stimuli, as would be associated with natural baits. The absence of natural baits removes the food reward for animals, such as dolphins and seals, reducing the risk of marine animals actively foraging around the fishing gear. The solid trigger traps were not as effective at capturing octopus as other trap types, despite their great success at catching the similar species O. djinda in Western Australia (Hart et al. 2016 ). The difference in capture results for these closely related octopus species may be due to alterations in hunting/foraging strategies employed by O. tetricus . Many octopus species have been shown to use a speculative hunting strategy when attacking crabs (Hanlon and Messenger 2018 ). That is, a strategy of first pouncing with outspread webbing and then feeling for food within (Yarnall 1969 ). This strategy used within the trigger trap would allow the triggering mechanism to be tripped, thus capturing the octopus. However, the low catch rates of O. tetricus in this experiment may be explained by their use of foraging strategies to explore the crab lure within. Octopus tetricus predominantly prey upon soft-sediment-shelled species (Anderson 1997 ; Godfrey-Smith and Lawrence 2012 ; Scheel et al. 2014 ; Scheel et al. 2017 ) in which they would employ a foraging strategy, not unlike the poke and crawl technique most frequently used by Octopus insularis (Leite et al. 2009 ). Octopuses in this experiment tended to display a poke-and-crawl approach to food and novel stimuli. This slower approach would provide ample time to investigate the crab lure and discover that it is not food. Consequently, there would be no reason to unnecessarily consume energy attacking the “non-food” object, thus not triggering the trap. Bait types Marine crustaceans are the most common prey in octopus diets (Ambrose 1984 ; Villanueva et al. 2017 ) due to their particular nutrient requirements of lipids and copper (Villanueva et al. 2017 ), and live crabs are often used as bait in octopus-targeted fishing methods (Yarnall 1969 ; Arreguín-Sánchez et al. 2000 ; Conners and Levine 2017 ; Sauer et al. 2019 ). Despite this, we found no influence of bait type on captures nor interactions with traps for O. tetricus (see also Leitão et al. 2021 ). Bait also did not influence octopuses’ activity, with the highest amount of octopus activity occurring during the trap trial (12.4%; plain crab lures used only), and the lowest activity during the bait trial (7.5%). These results may be explained by an octopuses’ perception of its prey. Octopuses are more likely to attack crabs and horizontal figures resembling a crab than more upright figures (Young 1956 ). Octopuses also show a preference for life-like artificial crabs with both the visual and tactile features of a real crab, as opposed to only visual, only tactile, or neither stimuli (Kawashima and Ikeda 2021 ). The artificial crabs used in this study met these requirements, therefore, the bait treatments (light, tuna oil, tuna bait pellet) may have been irrelevant and only the life-like resemblance of the crab lure was important. However, octopuses can discriminate between prey and non-prey via contact chemoreception (Buresch et al. 2022 ). The prey extracts used by Buresch et al. ( 2022 ) were shrimp and crab, which are common prey species of octopus. The tuna oil and bait may not have been appetising to the octopuses and therefore elicited a non-significant result. Future research should clarify the octopuses’ preference for varying species used as bait treatments. Behavioural interactions This experiment found the trigger trap to be the most attractive trap type to O. tetricus , recording significantly more interactions than any other trap. Of the six trap types presented, the trigger trap’s specifications may have been the most appropriate to fulfil the octopuses’ den requirements. Octopuses choose homes preferentially; assessing the dimensions and transparency of potential shelters and selecting the one that provides the best protection (Katsanevakis and Verriopoulos 2004 ). Octopuses have a preference for cavity length and diameter of dens (Mather 1982 ; Aronson 1986 ). Dens must meet a minimum requirement for cavity length to ensure the entire octopus is protected within, but no apparent maximum tolerable length (Aronson 1986 ). This is true for diameter too, with octopuses having a minimum diameter; based on the size of the octopus and thus ease of access into and out of the den, but no maximum diameter as octopuses can, and tend to, modify their habitats to suit their needs (Mather 1982 ; Aronson 1986 ; Anderson 1997 ; Scheel et al. 2014 ). Octopuses also show a preference for den material and select shelters that are solid and opaque in structure; probably to remain hidden and avoid predation or antagonistic interactions with conspecifics (Mather 1982 ; Anderson 1997 ; Katsanevakis and Verriopoulos 2004 ; Godfrey-Smith and Lawrence 2012 ). The trigger trap's attractive dimension specifications and failure to trigger would suggest that a simple octopus shelter pot of similar dimensions to the trigger trap may be more appropriate for targeting O. tetricus . This might be specifically useful for soft-sediment habitats, where artificial den enrichment increases octopus density compared to no impact on octopus density on rocky shores (Aronson 1986 ; Katsanevakis and Verriopoulos 2004 ). Activity patterns Octopuses are often sedentary animals, spending very little of their time away from the protection of their den (Katsanevakis and Verriopoulos 2004 ). In the current experiment, O. tetricus spent 90.5% of their time remaining in or near their den while in captivity. Octopus tetricus were, however, active 9.5% of the time, which was similar to the activity levels of 7.3% (Katsanevakis and Verriopoulos 2004 ) and 11% (Mather 1988 ) reported for O. vulgaris in the wild. In the present study, O. tetricus followed a diurnal activity pattern peaking in the morning daylight (0800–1200), with the lowest level of recorded activity during the dark hours of the very early morning (0000–0400). These results are similar to the activity pattern reported for O. insularis in the wild (O’Brien 2023), and support field observations by Godfrey-Smith and Lawrence ( 2012 ) and Scheel et al. ( 2017 ) who reported diurnal activity for O. tetricus . The activity pattern of O. tetricus differed from the nocturnal activity reported by Anderson ( 1997 ). Activity-based studies conducted on Enteroctopus dofleini (Mather et al. 1985 ), Octopus bimaculatus (Hofmeister and Voss 2017 ) and O. vulgaris (Dominguez-Lopez et al. 2021 ) showed highly variable activity among individuals with no discernible pattern. Variability was also found in the activity of three octopus species living in the same area of Hawaii and it is suggested that octopuses maintain temporal spacing and microhabitats to limit interspecific competition for food (Houck 1982 ). It is well known that octopuses exhibit high behavioural flexibility, and intelligence and are learning-focused, allowing them to be highly adaptable. Therefore, the dissimilarity observed in activity patterns, or lack thereof, among octopuses may be context-dependent and vary in different environments and conditions. The present study showed activity significantly varied among individuals and days, which may indicate the presence of personality in octopuses (Mather and Anderson 1993 ). Octopus personality was first suggested by Mather and Anderson ( 1993 ), who found that octopus temperaments included activity, reactivity, and avoidance that resembles the temperamental dimensions described for human infants (Buss and Plomin 1986 ), rhesus monkeys (Stevenson-Hinde et al. 1980 ), and stickleback fish (Huntingford 1976 ). Individual octopuses can consistently differ from one another in the degree of response or tendency to behave in a certain way, and related individuals are more similar than unrelated individuals in their degree and type of behaviour (Sinn et al. 2001 ). The individual octopuses in this experiment mostly exhibited behaviour that was consistent for each individual across multiple contexts and time, suggesting they had individual personalities (Pronk et al. 2010 ). Conclusion Octopus tetricus is being investigated as a new fisheries target species. The present study highlighted the targeted trap fishing methods that may be a viable approach. Here, the highest capture rates came from fine-mesh crab traps, and most interactions occurred with the solid trigger trap. This study also provided a clear view of the activity pattern of O. tetricus in an aquarium setting, supporting field observations of diurnal octopus activity in Eastern Australia (Godfrey-Smith and Lawrence 2012 ; Scheel et al. 2017 ). Octopus varied significantly in their responses to introduced traps and baits, with some bold individuals being captured multiple times and accounting for the bulk of interactions. In contrast, other octopus were more timid and rarely left their dens. Relative to many other fisheries species, octopus are highly intelligent animals with complex, flexible behaviour patterns. In light of this, it is important to consider the behavioural responses and wellbeing of octopuses in their interactions with fishing gear. Declarations Funding This project was supported by funding from the Fisheries Research and Development Corporation (Project No. 2020-008) on behalf of the Australian Government. Conflicts of interest The authors have no relevant financial or non-financial interests to disclose. Ethics approval Octopus collection, experiments and maintenance of live octopuses were performed under NSW DPI permit (P01/0059(A)-4.0) and followed the recommendations of the NSW DPI Ethics Committee (ACEC REF 22/01) in collaboration with Southern Cross University ACEC. Data/code availability The datasets generated during and/or analysed during the current study are available on reasonable request. Author Contributions Adam A. Vrandich: conceptualisation, investigation, visualisation, methodology, analysis, writing of the original manuscript draft, and subsequent review and editing. Karina Hall: conceptualisation, investigation, visualisation, methodology, analysis, funding acquisition, research supervision, writing – review and editing. Brendan P. Kelaher: investigation, funding acquisition, research supervision, writing – review and editing. References Ambrose RF (1984) Food preferences, prey availability, and the diet of Octopus bimaculatus Verrill. J Exp Mar Biol Ecol 77: 29-44. https://doi.org/10.1016/0022-0981(84)90049-2 Amodio P (2019) Octopus intelligence: The importance of being agnostic. 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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-4416218","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":303421650,"identity":"554be1dc-7497-40e2-9a25-b6d0f72189f1","order_by":0,"name":"Adam Anthony Vrandich","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA70lEQVRIiWNgGAWjYFCCBBgjsYGZoQJIMzM3kKLlDEgLI9FaEoCK20AMAlr425OfbmBsuydvzp7c+LlwXm00fztQy4+KbTi1SJx5ZnaDsa3YcGfPw2bpmduO5844zNjA2HPmNm5rbiSY3WA4k8C44UZiGzPvtmO5DUAtQBfi1iJ/I/0bSIs9RMucY7nzCWkxuJEDtKUiIRGipaEmdwMhLYZn3pTdSKhISN5wBugXnmMHcjcCtRzE5xe54+nbbnwwSLDdcDz94WeemrrceecPH3zwowKP90EgAcE8DCYP4FePCupIUTwKRsEoGAUjBAAAhJZiYqxfJ4QAAAAASUVORK5CYII=","orcid":"https://orcid.org/0009-0008-8952-1334","institution":"Southern Cross University National Marine Science Centre","correspondingAuthor":true,"prefix":"","firstName":"Adam","middleName":"Anthony","lastName":"Vrandich","suffix":""},{"id":303421651,"identity":"ec98b2e1-5e09-4798-837b-66fce6e3abdc","order_by":1,"name":"Brendan P Kelaher","email":"","orcid":"","institution":"Southern Cross University National Marine Science Centre","correspondingAuthor":false,"prefix":"","firstName":"Brendan","middleName":"P","lastName":"Kelaher","suffix":""},{"id":303421652,"identity":"b01ca1c5-3bd9-419b-9287-4f9f7bd5046d","order_by":2,"name":"Karina Hall","email":"","orcid":"","institution":"New South Wales Department of Primary Industries","correspondingAuthor":false,"prefix":"","firstName":"Karina","middleName":"","lastName":"Hall","suffix":""}],"badges":[],"createdAt":"2024-05-14 03:37:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4416218/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4416218/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00227-024-04534-y","type":"published","date":"2024-10-14T15:57:14+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":57450095,"identity":"57e6c0bf-d17e-4457-bd11-93acaa14a14b","added_by":"auto","created_at":"2024-05-30 20:15:57","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":88733,"visible":true,"origin":"","legend":"\u003cp\u003eTotal number of interactions by octopus with each trap type during the trap trial, broken down according to interaction type (A) and with times spent captured within traps removed (B), given that octopus were unable to interact with any other trap while captured. Similar data for the bait trials were pooled across all bait types (C, D) and with bait types separated (E, F). Numbers of captures are indicated in parentheses above relevant columns.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4416218/v1/f7d150eef3e6b46f87e767ea.png"},{"id":57450096,"identity":"de9f8163-b890-42d4-9f30-46430257e227","added_by":"auto","created_at":"2024-05-30 20:15:58","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":200473,"visible":true,"origin":"","legend":"\u003cp\u003ePredicted frequencies of total combined active behaviours during each time period across all three trials. Octopuses were most active during the morning from 0800 - 1200 and night from 1600 – 2000 and were least active during the dark hours of the very early morning from 0000 – 0400. The median and mean values are represented by the bold black line and yellow dot within the box plot, respectively.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4416218/v1/feff38cde9d44447d5c502b5.jpeg"},{"id":57450423,"identity":"e72719aa-c7ba-4c46-b166-84166aa309ce","added_by":"auto","created_at":"2024-05-30 20:23:58","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":170633,"visible":true,"origin":"","legend":"\u003cp\u003ePredicted frequencies of trap-associated active behaviours for each time period during the bait trials. Octopuses were most active during the day (0800 – 1600; i.e. morning and afternoon) and night from 0800 – 2000 and were the least active during the dark hours of the very early morning (0000 – 0400). The median and mean values are represented by the bold black line and yellow dot within the box plot, respectively\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4416218/v1/c5bf04c3c9c69ca5c25295d2.jpeg"},{"id":67149725,"identity":"d3c25157-4912-44bd-8253-0e9c965e90bd","added_by":"auto","created_at":"2024-10-21 16:13:49","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1009654,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4416218/v1/baf57e7d-4b0c-46a9-8989-59746f72bc39.pdf"}],"financialInterests":"","formattedTitle":"Behavioural patterns of Octopus tetricus (Mollusca: Cephalopoda) and their responses to fisheries trap and bait combinations","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCephalopods have become an increasingly valuable commodity, with interest growing in their use as a sustainable food source and as an important future food supply under climate change (Willer et al. \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). During the last 50 years, there has been a 416% increase in cephalopod wild-caught fisheries landings, which reached a peak of 4\u0026nbsp;million tonnes in 2013 (Ospina-Alvarez et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). While many traditional finfish stocks are either fully fished or in decline (FAO \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), cephalopod populations are generally thought to be increasing either in response to climate change or a reduced abundance of predators or a combination of these or similar factors (Doubleday et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Nonetheless, the overexploitation of cephalopod species has occurred in some parts of the world and developing fisheries require appropriate management to ensure sustainability (Ospina-Alvarez et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Furthermore, as evidence for potential sentience and the capacity to feel pain among cephalopods accumulates, which is particularly the case for octopuses, there has been increased scrutiny regarding animal welfare with respect to capture and culture methods (Mather and Anderson \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; King and Marino \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eOctopuses exhibit behavioural flexibility and many attributes suggestive of high intelligence. Although these attributes alone are insufficient evidence of complex cognition (Emery and Clayton \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Amodio \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), they are considered precursors for many associated capacities, such as causal reasoning, imagination, and mental attribution (Schnell et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Octopuses also exhibit introspection, a cognitive process used to evaluate consciousness (Mather and Andrade \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2023\u003c/span\u003e); this process involves internally evaluating sensory input and making decisions before taking action. Furthermore, as Mather and Anderson (\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) and Mather (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) suggest, octopuses can feel pain and display adverse behaviour in response to stress. The stress response systems in octopuses and vertebrates are neuronally and endocrinologically similar (Stefano et al. \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2002\u003c/span\u003e), with octopuses showing consistent behavioural responses to pain in humans (Mather and Anderson \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Therefore, it is important to recognise the need to adopt a more robust ethical approach when dealing with such cognitively advanced invertebrates (King and Marino \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), especially regarding fishing and culture methods that could induce either pain or stress.\u003c/p\u003e \u003cp\u003eOther octopus behavioural attributes of direct relevance to fisheries biology are daily activity patterns and personality types. While traditionally thought to be mostly nocturnal, the activity patterns of octopuses are quite varied (Meisel et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2013\u003c/span\u003e); with contrasting daily activity patterns now documented for closely related species (Meisel et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2006\u003c/span\u003e), among species inhabiting the same area (Houck \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1982\u003c/span\u003e), and within species (Kayes \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1973\u003c/span\u003e; Mather \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Meisel et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). The presence of individual personality has also been described in octopuses. Three aspects of octopus temperament (activity, reactivity, and avoidance) show remarkable resemblance to those described for vertebrates (Mather and Anderson \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). Furthermore, individual octopus behavioural tendencies can change over time, possibly due to lived experience and learning (Sinn et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Sinn and Moltschaniwskyj \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2005\u003c/span\u003e), and octopus behavioural traits can be inherited (Sinn et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). There is, therefore, scope for static fishing gears, like traps, to alter the personality frequencies within exploited populations through fishing-induced evolution driven by the differential removal of bold or active individuals (Uusi-Heikkil\u0026auml; et al. 2008).\u003c/p\u003e \u003cp\u003eFisheries targeting species of octopus using selective gears, which produce little or no bycatch or discards, are generally considered more sustainable, economical, and environmentally friendly than those deploying non-selective gears (Petetta et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Enclosed static gears (like soaked pots and traps) tend to exhibit higher species- and size-selectivity of entrapment than active towed gears (like bottom trawls) or exposed static nets (like trammel nets, gill nets, fixed nets, and bottom set nets). Pots and traps also tend to have high survival rates for the bycatch that is incidentally caught (Kopp et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Conversely, actively towed gears and exposed static nets used in mixed-species fisheries produce significant bycatch. These fisheries pose a threat to large marine vertebrates (Ferretti et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Casale \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), mammals (Bearzi \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2002\u003c/span\u003e) and fish (Monteiro et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2001\u003c/span\u003e), who are entangled and captured as bycatch. Non-selective fishing gears exhibit significantly high discard rates with bottom-trawl fisheries responsible for the bulk of discards globally (Zeller et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Alternatively, marine animals captured in pot and trap fishing gear are often alive and uninjured upon retrieval, so if undersized can be released alive, and if legal can demand a higher market price (Kopp et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Hence, selective fishing methods for octopus are more ethical to the target species and more economical for individual fishers.\u003c/p\u003e \u003cp\u003eIn Australia, octopuses have been taken as bycatch in multi-species trawl fisheries and more recently have become a target species. Targeted trapping for octopus first started in 2001 with the development of the Western Australian Octopus Interim Managed Fishery (WAOIMF; Hart et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). This fishery targets \u003cem\u003eOctopus djinda\u003c/em\u003e (previously known as \u003cem\u003eOctopus cf. tetricus\u003c/em\u003e; Amor and Hart \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and developed an active trigger trap (with a snap closing entrance door), which produced a\u0026thinsp;~\u0026thinsp;400% increase in octopus catch (from 33 t in 2009 to 170 t in 2010) compared to the previously used shelter pots (Hart et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The success of the WAOIMF sparked exploration of similar opportunities for the Eastern Australian octopus species \u003cem\u003eOctopus tetricus\u003c/em\u003e in New South Wales (NSW). \u003cem\u003eOctopus tetricus\u003c/em\u003e is a medium-sized, robust species with an arm span reaching up to 2 m (Hall and Moltschaniwskyj in press). It mainly inhabits rocky reefs, shallow seagrass beds, and sediment substrates (Anderson \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1997\u003c/span\u003e), and utilises dens for refuge from predation (Anderson \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1997\u003c/span\u003e), mating (Godfrey-Smith and Lawrence \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Caldwell et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), and egg rearing (Garci 2016). \u003cem\u003eOctopus tetricus\u003c/em\u003e completes its life cycle within one to two years (Ramos et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) and employs a semelparous reproductive strategy (Anderson et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2002\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe rapid growth and relatively short life span of \u003cem\u003eO. tetricus\u003c/em\u003e potentially makes it an appropriate target species (Kelaher et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). However, there is currently insufficient biological and fisheries knowledge of \u003cem\u003eO. tetricus\u003c/em\u003e to determine whether current catch levels are sustainable and whether further targeted fishing is feasible. In addition, it is not known whether common shelter pots that allow octopus to enter and leave (for feeding) are effective for catching \u003cem\u003eO. tetricus\u003c/em\u003e or whether the WA trigger traps developed for \u003cem\u003eO. djinda\u003c/em\u003e are appropriate to catch the smaller \u003cem\u003eO. tetricus\u003c/em\u003e. Furthermore, the species\u0026rsquo; activity patterns are likely to influence trapping catch rates and appropriate soak times, and these require further clarification in \u003cem\u003eO. tetricus\u003c/em\u003e. To address this, we (1) investigated the behavioural response of \u003cem\u003eO. tetricus\u003c/em\u003e to different combinations of trap designs and lures/baits; (2) designed and tested a novel ethical octopus trap; and (3) investigated the daily activity patterns of \u003cem\u003eO. tetricus\u003c/em\u003e.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eCollection, transportation, and acclimation of octopus\u003c/h2\u003e \u003cp\u003eEight \u003cem\u003eO. tetricus\u003c/em\u003e were captured within research survey crab traps at Lake Macquarie, NSW (-33.0311, 151.5603) and by hand at Sawtell, NSW (-30.376607, 153.101589). Each octopus was transported to the National Marine Science Centre (NSMC, Coffs Harbour, Australia \u0026minus;\u0026thinsp;30.2677 S, 153.1374 E) inside an individual 20-L bucket with mesh windows for water exchange that were placed into two 340-L insulated transporters at a stocking density of up to four octopuses each. The transporters were filled on-site with fresh seawater and kept aerated via a supply of diffuse pure oxygen. At the NMSC, the octopuses were transferred inside the buckets into 68-L plastic bins for acclimation to the mesocosm water over 3 h via gradual water transfer. The octopuses were provided a minimum seven-day settlement period to recover from transportation stress and acclimate to their new tank environment. There were no mortalities or obvious injuries during capture, transport, and acclimatisation to the mesocosms.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eMesocosms and experimental setup\u003c/h2\u003e \u003cp\u003eEach octopus was individually housed in a 3000-L mesocosm comprising a fibreglass tank (2200 mm diameter \u0026times; 800 mm height) furnished with a central habitat of pebble substrate, two artificial dens (terracotta pots), artificial plants and empty oyster shells. The tanks were located outdoors under a solid awning to protect against direct sunlight and rain. Each tank was supplied with flow-through ambient seawater pumped directly from the adjacent ocean at ambient temperature (ranging from 16.1\u0026ndash;23.0 ℃, May to August 2022). Each mesocosm was monitored via a 24-h video surveillance system (Reolink: RLK16-810B8-A) with a 6 TB internal hard drive which was backed up daily. To ensure octopuses were visible at night, two infrared floodlights (Infront Technologies: IFT-IR80-96) were installed to the rim of each tank. It should be noted that octopuses exhibited no pupillary response to infrared light during a study conducted by Soto et al. (\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), suggesting octopuses are not able to see infrared light.\u003c/p\u003e \u003cp\u003eAfter acclimation, each octopus was anaesthetised by immersion in a bath of magnesium chloride of 3.25% concentration (MgCl, 32.5 g. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). The dosage was increased from the recommended 2.70% concentration (27 g. L-1, as recommended by the Department of Primary Industries 2015) due to insufficient anaesthesia after ~\u0026thinsp;13 minutes of submersion. On average, octopuses required 15 minutes of submersion in the stronger MgCl solution to be sufficiently sedated. Once anaesthetised, each octopus was weighed, and its dorsal mantle length (DML) was measured. Each octopus was then injected in the base of the third left arm with a fluorescent dye (oxytetracycline, OTC, 50 mg. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e solution administered at 100 mg. Kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e body weight), to mark internal hard structures and a passive integrated transponder (PIT) microchip tag (weighing 0.01 g, at 2 \u0026times; 11 mm) was inserted via a hypodermic needle into the subcutaneous tissue between the first and second left arm of the octopus. These latter procedures were completed for a related study, with the results reported elsewhere. The octopuses were then submerged in a fresh seawater bath with an aerator for recovery before return to mesocosms.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eExperimental trials\u003c/h2\u003e \u003cp\u003eExperiments to test hypotheses about trap and bait effectiveness began in July 2022. Twenty-four-hour video footage of the octopuses (n\u0026thinsp;=\u0026thinsp;8) was collected for three days under normal mesocosm conditions before traps were introduced. This provided a baseline for behaviours and activity levels of each octopus that might influence their response during the subsequent trap and bait trials. Twenty-four-hour video footage was then collected for the duration of each of the following trap and bait trials.\u003c/p\u003e \u003cp\u003eAn initial trap trial was completed over seven days (168 h) to assess each octopuses\u0026rsquo; behavioural responses to five different trap types that were introduced on the first day: (1) solid trigger trap; (2) fine-mesh crab trap; (3) novel oyster trap; (4) single-entrance PVC pipe; and (5) double-entrance PVC pipe (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Figure S1). One of each of these five traps were placed in each tank with the trap entrances equidistant from the central habitat to avoid proximity bias. All were baited with a plain artificial orange plastic crab lure (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Figure S2). If an octopus was caught it was released at feeding times (between 0900\u0026ndash;1000) each day. If an octopus was captured again during that day, they were left until the next day to assess the trap\u0026rsquo;s capacity to prevent escape. The trigger trap was excluded from this condition, given that escape was not possible from this trap type and did not allow water exchange into the trap once it was triggered. Therefore, octopuses were released from trigger traps as soon as possible after capture. Upon conclusion of the trial, all traps were removed, and the octopuses were given a 5-day recovery period.\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\u003eDescription of the trap types used in the experiment\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTrap Type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDescription\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTrigger trap\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWA solid plastic trigger trap.\u003c/p\u003e \u003cp\u003eDimensions: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(620 \\text{m}\\text{m}\\times 220 \\text{m}\\text{m}\\times 280 \\text{m}\\text{m} (\\text{L}\\times \\text{W}\\times \\text{H})\\)\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrab trap\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCustom fine-mesh, round crab trap with three funnel entrances. \u003c/p\u003e \u003cp\u003eDimensions: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(700 \\text{m}\\text{m} {\\varnothing}, 18 \\text{m}\\text{m} \\text{m}\\text{e}\\text{s}\\text{h}\\)\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOyster trap\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCustom mesh shelter pot.\u003c/p\u003e \u003cp\u003eDimensions: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(460 \\text{m}\\text{m}\\times 230 \\text{m}\\text{m} {\\varnothing}; 5 \\text{m}\\text{m} \\text{m}\\text{e}\\text{s}\\text{h}\\)\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSingle-entrance shelter pot\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCustom single-entrance shelter pot. Polyvinyl chloride (PVC) pipe. Dimensions: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(500 \\text{m}\\text{m}\\times 100 \\text{m}\\text{m} {\\varnothing}\\)\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDouble-entrance shelter pot\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCustom double entrance shelter pot. PVC straight pipe \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(300 \\text{m}\\text{m}\\times 100 \\text{m}\\text{m} {\\varnothing}\\)\u003c/span\u003e\u003c/span\u003e with a PVC \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(45^\\circ\\)\u003c/span\u003e\u003c/span\u003ejunction \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(100 \\text{m}\\text{m} {\\varnothing}\\)\u003c/span\u003e\u003c/span\u003e. Overall length: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(520 \\text{m}\\text{m}\\)\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHybrid trap\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNovel trap design: a combination of the (1) trigger and (2) crab traps. A cylinder-shaped mesh trap with a shelter pot base and crab trap entrance. Dimensions: 590\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{m}\\text{m}\\times 240 \\text{m}\\text{m} {\\varnothing}; 5 \\text{m}\\text{m} \\text{m}\\text{e}\\text{s}\\text{h}\\)\u003c/span\u003e\u003c/span\u003e.\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 \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDescription of the lure/bait types used in the experiment\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBait type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDescription\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlain\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA clean, plain silicone crab lure.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSilicone crab lure with an LED light attached.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTuna oil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA silicone crab lure smothered in Tuna oil (store-bought from a fishing and tackle shop).\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTuna bait pellet\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA silicone crab lure with a tune bait pellet stuffed inside the lure.\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\u003eThe bait trials consisted of three consecutive trials lasting 72 h each with at least 24 h recovery period between trials. During each trial, the octopuses\u0026rsquo; behavioural responses to a single, randomly assigned trap type with different lure/bait type combinations were assessed. This was achieved by placing four of the same trap type in each tank, with each trap containing a different lure/bait type. Results from the first trap trial informed the decision to include only the most successful traps (i.e., trigger-, crab-, and a novel hybrid trap) in the bait trials (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The novel hybrid trap was designed to include design elements that appealed to the hunting and sheltering instincts of octopus. The four bait types used in the experiment included: (1) a plain artificial orange plastic crab lure; (2) crab with LED light; (3) crab with tuna oil; and (4) crab with tuna bait-pellet (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Figure S2). The crab with LED light is the current bait type used in the WA OIMF and is being trialled in the NSW developmental octopus fishery. The tuna oil (3) and tuna bait pellet (4) treatments were suggested by commercial fishers as possible enhancements to improve catch rates in commercial fishing. The placement of lure/bait types within the tank was randomised to avoid learning or proximity bias.\u003c/p\u003e \u003cp\u003eAt the end of the experiment, each octopus was euthanized in a bath of 7.5% MgCl and dissected to remove all hard structures (statoliths, stylets and beaks) and a tissue sample for later ageing and genetic analysis (reported elsewhere) and record other biological information, such as sex and reproductive stage.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eBehavioural analyses\u003c/h2\u003e \u003cp\u003eFor each of the three experiments, a time budget and frequency counts of specific behaviours of interest (see SI Table S1) were used to quantify the activity patterns of each octopus and their responses to the trap and lure/bait types. A total of 18 behaviours were considered (see SI Table S1) based on pre-experiment observations of the octopuses and previous studies and ethograms of the same or similar octopus species (Mather and Alupay \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Dominguez-Lopez et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Behaviours were grouped into four main categories: den-associated-, other-active-, trap-associated- and other behaviours. At the end of each trial, all video footage of the octopuses was examined using 2-minute interval focal sampling. This involved observing and recording the behaviour of each individual octopus every 2 minutes for the entirety of the experiment. This produced 93,044 total observation data points.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eData analyses\u003c/h2\u003e \u003cp\u003eAll data analyses were performed using R version 4.2.2 (R Core Team 2022). Generalised Linear Mixed Models (GLMMs) from the \u0026lsquo;lme4\u0026rsquo; package (Bates \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) were used to test hypotheses about the influence of different combinations of fixed and random explanatory variables on: (a) the number of octopus captures; (b) the behavioural responses (number of interactions) of \u003cem\u003eO. tetricus\u003c/em\u003e with different trap and bait combinations; and (c) the daily activity patterns of \u003cem\u003eO. tetricus\u003c/em\u003e. This was achieved by fitting a random-effects base-model, followed by forward selection of fixed factors and relevant interaction terms. Model fits were compared using likelihood ratio tests (chi-squared goodness of fit and corresponding p-value) and Akaike Information Criteria (AICs) for each combination of models. The explanatory power of the random effects was assessed using the level of variation (\u003cem\u003evar.\u003c/em\u003e) explained in the base model. As bait was not found to explain significant variation in any trials, data from the two trap trials were pooled to increase the power for testing the significant influence of other effects. Finally, post-hoc Tukey\u0026rsquo;s pairwise comparisons were used to: (a) test for differences in number of captures among trap types; (b) determine the influence of trap types on the number of interactions; (c) test for differences in activity levels during different times of the day (Time Periods, see below).\u003c/p\u003e \u003cp\u003eThe octopus capture data were analysed using binomial logistic regression models, with capture or not as the binomial response variable and a logit link function. Trap type and bait type were included as fixed effects, and tank number (i.e., individual octopuses with varying personalities) and day number (nested within trial number) were included as random effects. The octopuses\u0026rsquo; trap-associated behaviours (see SI Table S1) were analysed to determine the frequency of octopus interactions with different trap and bait combinations. For these analyses, the response variable was the frequency (count) of 2-min intervals that included interactive behaviours and, like most categorical behavioural data, included a high proportion of zeros. Therefore, negative binomial models with a logit link were fit to these count data, due to overdispersion with the Poisson distribution. Trap-type and bait-type were included as fixed factors and tank number, and day number (nested within trial number) were included as random effects.\u003c/p\u003e \u003cp\u003eFor the activity pattern analyses, only active behaviours were analysed, which included other-active and trap-associated active behaviours (see SI Table S1), and total combined activity and excluded den-associated behaviours. These count data were also fitted with negative binomial models with a log link function, because of overdispersion with the Poisson distribution. These activity data were analysed for the influence of a fixed factor \u0026lsquo;time period\u0026rsquo;, created by dividing each day into six time intervals: very early morning (0000\u0026ndash;0400), dawn (0400\u0026ndash;0800), morning (0800\u0026ndash;1200), afternoon (1200\u0026ndash;1600), dusk (1600\u0026ndash;2000), and night (2000\u0026ndash;2400). Random effects included tank number and day number (nested within trial number).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eOctopus capture\u003c/h2\u003e \u003cp\u003eA total of 30 captures occurred across all four trials, with two octopuses accounting for most of the captures (i.e., one octopus was captured 15 times, and another octopus was captured 9 times). Of the remaining six octopuses: two were caught twice, two were caught once and two were not caught at all. Trap type had a significant influence on the number of captures in all trials (GLMM; trap trial: \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;7.56, df\u0026thinsp;=\u0026thinsp;1, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0059; bait trials: \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;13.15, df\u0026thinsp;=\u0026thinsp;2, \u003cem\u003ep\u0026thinsp;=\u003c/em\u003e\u0026thinsp;0.0013; combined trials: \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;32.05, df\u0026thinsp;=\u0026thinsp;3, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). The crab trap accounted for the largest number of octopus captures (23) across all trials, with a 10% probability of capturing an octopus (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The crab trap was more successful than the hybrid (Tukey\u0026rsquo;s; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0379) and trigger (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0012) traps, which captured one and two octopus respectively, with a 1% probability of capture for each of these two trap types (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The oyster trap captured four octopuses in total, however, 100% of caught octopuses escaped within 2 minutes of capture, given that it had a permanent opening. One of the octopus caught in the trigger trap had an arm severed in the closing mechanism and subsequently died. Octopuses caught during the bait trial were spread evenly among the bait types, with no significant influence of bait type on octopus capture (GLMM; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.84).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eNumber of captures for each trap type, including capture and escape probabilities\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCapture\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e \u003cp\u003eTrap Type\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTrigger trap\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCrab trap\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOyster trap\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHybrid trap\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e244\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e223\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e191\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes (1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCapture Probability\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo. of escapes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEscape probability\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eBehavioural interactions\u003c/h3\u003e\n\u003cp\u003eThe greatest frequency of interactions among octopuses and traps were recorded for those captured within a crab trap (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). However, during those periods the octopuses were prevented from interacting with any other trap or bait types or interacting with the crab trap using a different behavioural response. Therefore, these interactions were excluded from further data analyses, which left, a total of 3,862 interactions across the four trials. Two octopus were responsible for ~\u0026thinsp;60% of the remaining interactions (i.e., one octopus underwent 1,596 interactions and another octopus made 760 interactions), which resulted in significant variation among individuals (tank number) and days in the number of octopus interactions with traps during the first trap trial (GLMM random-effects model; tank number: \u003cem\u003evar.\u003c/em\u003e = 1.11, day number: \u003cem\u003evar.\u003c/em\u003e = 0.63; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0019). The frequency of octopus interactions with traps also depended significantly on trap type (GLMM; \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;64.81, df\u0026thinsp;=\u0026thinsp;4, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), with significantly more interactions with trigger traps than any other trap type once captures in crab traps were removed (Tukey\u0026rsquo;s; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), with an average of 43 interactions per observation combination. For the bait trial, there was no significant effect of trap nor bait type on the number of interactions (GLMM; trap type: \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0869; bait type: \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.4716). There was also no significant variation among tanks nor days once captures in crab traps were removed (GLMM random-effects model: \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.31).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eActivity patterns\u003c/h2\u003e \u003cp\u003eOctopus activity levels ranged from ~\u0026thinsp;4% to ~\u0026thinsp;30%, with the rest of the time spent in their dens. On average, octopuses spent 9.5% of their time active. Activity patterns of octopuses differed significantly among individuals (tank number) and days within trials, but not among trials (GLMM random-effects model; tank number: \u003cem\u003evar.\u003c/em\u003e = 0.4344; day number | trial number: \u003cem\u003evar.\u003c/em\u003e = 0.1347; trial number: \u003cem\u003evar.\u003c/em\u003e \u0026lt; 0.0001; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). Octopuses spent the largest proportion of their time active during the second day (10.7%) of the pre-trial, and the final day (23.3%) of the trap trial and were the least active on the second day (4.1%) of the trap trial. An octopuses\u0026rsquo; total combined activity was significantly influenced by time of day (GLMM; \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;29.272, df\u0026thinsp;=\u0026thinsp;29.27, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The highest level of activity occurred in the morning daylight (0800\u0026ndash;1200) and at dusk (1600\u0026ndash;2000); spending\u0026thinsp;~\u0026thinsp;14% and ~\u0026thinsp;11% of their time being active during these time periods, respectively. Octopuses were mostly inactive during the dark hours of the very early morning (0000\u0026ndash;0400), with only\u0026thinsp;~\u0026thinsp;6% of their time spent being active. They were significantly more active during morning daylight, from 0800\u0026ndash;1200, than during the dark hours of the very early morning, from 0000\u0026ndash;0400 (Tukey's; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), dawn, from 0400\u0026ndash;0800 (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0177) and during the afternoon, from 1200\u0026ndash;1600 (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0460).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDuring the bait trials, an octopuses\u0026rsquo; trap-associated activity was also significantly influenced by time of day (GLMM; \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;25.805, df\u0026thinsp;=\u0026thinsp;5, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001; Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), whereas other-activity was not (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.3377). Octopuses interacted with traps mostly in daylight, from 0800\u0026ndash;1600 (morning and afternoon; 5.5%), and the least interactions occurred while it was dark, from 0000\u0026ndash;0400 (very early morning; 1%), and during dawn, from 0400\u0026ndash;0800 (1%). An octopuses\u0026rsquo; trap-associated activity was significantly higher in the morning daylight from 0800\u0026ndash;1200 than in the dark hours of the very early morning from 0000\u0026ndash;0400 (Tukey's; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) and dawn from 0400\u0026ndash;0800 (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0035). Trap-associated activity was significantly lower in the dark hours of the very early morning (0000\u0026ndash;0400) than in daylight (0800\u0026ndash;1600; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0186) and during dusk (1600\u0026ndash;2000; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0060).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe 24 h surveillance of \u003cem\u003eO. tetricus\u003c/em\u003e allowed us to observe and analyse their activity patterns and behavioural responses to proposed fishing gear. We found fine-mesh crab traps to be the most successful at octopus capture, while the solid trigger traps were the most attractive to octopus exploration. Contrary to expectation, the capture rates, behavioural interactions with traps and the activity patterns of octopuses were not significantly influenced by bait type. In general, octopuses were mostly sedentary and stayed within or near their established dens (terracotta pots). When they were active, octopuses demonstrated diurnal activity, peaking in the morning daylight (0800\u0026ndash;1200), with the lowest activity during the dark hours of the very early morning (0000-0400).\u003c/p\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eOctopus capture\u003c/h2\u003e \u003cp\u003eThe success of the crab trap in capturing \u003cem\u003eO. tetricus\u003c/em\u003e may be due to the methods employed by octopuses to explore novel objects. Octopuses typically use visual and tactile exploration to investigate novel objects, but only tactile assessment of known objects (Ovalle et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Of the three trap types, the fine mesh of the crab traps allowed for the greatest visual exploration of the artificial lure from all angles and any distance. Octopuses can change their hunting strategies to adapt to their current environment and have been shown to be visual opportunists (Leite et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Therefore, the transparent nature of the crab traps may spark opportunistic visual attacks by octopuses on a highly visible lure. Octopus are a well-known bycatch species in static gears that utilise a mesh structure such as the barrel-shaped lobster pots used in the South African Spiney Lobster fishery (Groeneveld et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) and the beehive pots employed by the South Australian Southern Rock Lobster fishery (Brock and Ward \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). Although the most successful at capture, crab traps can pose significant problems when deployed in the wild. Crab traps deployed with natural baits are known for high bycatch rates and can cause mortality of dolphins (Tursiops truncates; Burdett and McFee \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), seals (Kovacs et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) and turtles (Dorcas et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Artificial lures may present a solution; during our trap trial, the crab traps were effective at capturing octopus with a plain bright orange crab artificial lure, which presented only visual and no olfactory stimuli, as would be associated with natural baits. The absence of natural baits removes the food reward for animals, such as dolphins and seals, reducing the risk of marine animals actively foraging around the fishing gear.\u003c/p\u003e \u003cp\u003eThe solid trigger traps were not as effective at capturing octopus as other trap types, despite their great success at catching the similar species \u003cem\u003eO. djinda\u003c/em\u003e in Western Australia (Hart et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The difference in capture results for these closely related octopus species may be due to alterations in hunting/foraging strategies employed by \u003cem\u003eO. tetricus\u003c/em\u003e. Many octopus species have been shown to use a speculative hunting strategy when attacking crabs (Hanlon and Messenger \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). That is, a strategy of first pouncing with outspread webbing and then feeling for food within (Yarnall \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e1969\u003c/span\u003e). This strategy used within the trigger trap would allow the triggering mechanism to be tripped, thus capturing the octopus. However, the low catch rates of \u003cem\u003eO. tetricus\u003c/em\u003e in this experiment may be explained by their use of foraging strategies to explore the crab lure within. \u003cem\u003eOctopus tetricus\u003c/em\u003e predominantly prey upon soft-sediment-shelled species (Anderson \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Godfrey-Smith and Lawrence \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Scheel et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Scheel et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) in which they would employ a foraging strategy, not unlike the poke and crawl technique most frequently used by \u003cem\u003eOctopus insularis\u003c/em\u003e (Leite et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Octopuses in this experiment tended to display a poke-and-crawl approach to food and novel stimuli. This slower approach would provide ample time to investigate the crab lure and discover that it is not food. Consequently, there would be no reason to unnecessarily consume energy attacking the \u0026ldquo;non-food\u0026rdquo; object, thus not triggering the trap.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eBait types\u003c/h2\u003e \u003cp\u003eMarine crustaceans are the most common prey in octopus diets (Ambrose \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1984\u003c/span\u003e; Villanueva et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) due to their particular nutrient requirements of lipids and copper (Villanueva et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), and live crabs are often used as bait in octopus-targeted fishing methods (Yarnall \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e1969\u003c/span\u003e; Arregu\u0026iacute;n-S\u0026aacute;nchez et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Conners and Levine \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Sauer et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Despite this, we found no influence of bait type on captures nor interactions with traps for \u003cem\u003eO. tetricus\u003c/em\u003e (see also Leit\u0026atilde;o et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Bait also did not influence octopuses\u0026rsquo; activity, with the highest amount of octopus activity occurring during the trap trial (12.4%; plain crab lures used only), and the lowest activity during the bait trial (7.5%). These results may be explained by an octopuses\u0026rsquo; perception of its prey. Octopuses are more likely to attack crabs and horizontal figures resembling a crab than more upright figures (Young \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e1956\u003c/span\u003e). Octopuses also show a preference for life-like artificial crabs with both the visual and tactile features of a real crab, as opposed to only visual, only tactile, or neither stimuli (Kawashima and Ikeda \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The artificial crabs used in this study met these requirements, therefore, the bait treatments (light, tuna oil, tuna bait pellet) may have been irrelevant and only the life-like resemblance of the crab lure was important. However, octopuses can discriminate between prey and non-prey via contact chemoreception (Buresch et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The prey extracts used by Buresch et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) were shrimp and crab, which are common prey species of octopus. The tuna oil and bait may not have been appetising to the octopuses and therefore elicited a non-significant result. Future research should clarify the octopuses\u0026rsquo; preference for varying species used as bait treatments.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eBehavioural interactions\u003c/h2\u003e \u003cp\u003eThis experiment found the trigger trap to be the most attractive trap type to \u003cem\u003eO. tetricus\u003c/em\u003e, recording significantly more interactions than any other trap. Of the six trap types presented, the trigger trap\u0026rsquo;s specifications may have been the most appropriate to fulfil the octopuses\u0026rsquo; den requirements. Octopuses choose homes preferentially; assessing the dimensions and transparency of potential shelters and selecting the one that provides the best protection (Katsanevakis and Verriopoulos \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). Octopuses have a preference for cavity length and diameter of dens (Mather \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Aronson \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1986\u003c/span\u003e). Dens must meet a minimum requirement for cavity length to ensure the entire octopus is protected within, but no apparent maximum tolerable length (Aronson \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1986\u003c/span\u003e). This is true for diameter too, with octopuses having a minimum diameter; based on the size of the octopus and thus ease of access into and out of the den, but no maximum diameter as octopuses can, and tend to, modify their habitats to suit their needs (Mather \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Aronson \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Anderson \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Scheel et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Octopuses also show a preference for den material and select shelters that are solid and opaque in structure; probably to remain hidden and avoid predation or antagonistic interactions with conspecifics (Mather \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Anderson \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Katsanevakis and Verriopoulos \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Godfrey-Smith and Lawrence \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The trigger trap's attractive dimension specifications and failure to trigger would suggest that a simple octopus shelter pot of similar dimensions to the trigger trap may be more appropriate for targeting \u003cem\u003eO. tetricus\u003c/em\u003e. This might be specifically useful for soft-sediment habitats, where artificial den enrichment increases octopus density compared to no impact on octopus density on rocky shores (Aronson \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Katsanevakis and Verriopoulos \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eActivity patterns\u003c/h2\u003e \u003cp\u003eOctopuses are often sedentary animals, spending very little of their time away from the protection of their den (Katsanevakis and Verriopoulos \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). In the current experiment, \u003cem\u003eO. tetricus\u003c/em\u003e spent 90.5% of their time remaining in or near their den while in captivity. \u003cem\u003eOctopus tetricus\u003c/em\u003e were, however, active 9.5% of the time, which was similar to the activity levels of 7.3% (Katsanevakis and Verriopoulos \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) and 11% (Mather \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e1988\u003c/span\u003e) reported for \u003cem\u003eO. vulgaris\u003c/em\u003e in the wild. In the present study, \u003cem\u003eO. tetricus\u003c/em\u003e followed a diurnal activity pattern peaking in the morning daylight (0800\u0026ndash;1200), with the lowest level of recorded activity during the dark hours of the very early morning (0000\u0026ndash;0400). These results are similar to the activity pattern reported for \u003cem\u003eO. insularis\u003c/em\u003e in the wild (O\u0026rsquo;Brien 2023), and support field observations by Godfrey-Smith and Lawrence (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) and Scheel et al. (\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) who reported diurnal activity for \u003cem\u003eO. tetricus\u003c/em\u003e. The activity pattern of \u003cem\u003eO. tetricus\u003c/em\u003e differed from the nocturnal activity reported by Anderson (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). Activity-based studies conducted on \u003cem\u003eEnteroctopus dofleini\u003c/em\u003e (Mather et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e1985\u003c/span\u003e), \u003cem\u003eOctopus bimaculatus\u003c/em\u003e (Hofmeister and Voss \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) and \u003cem\u003eO. vulgaris\u003c/em\u003e (Dominguez-Lopez et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) showed highly variable activity among individuals with no discernible pattern. Variability was also found in the activity of three octopus species living in the same area of Hawaii and it is suggested that octopuses maintain temporal spacing and microhabitats to limit interspecific competition for food (Houck \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1982\u003c/span\u003e). It is well known that octopuses exhibit high behavioural flexibility, and intelligence and are learning-focused, allowing them to be highly adaptable. Therefore, the dissimilarity observed in activity patterns, or lack thereof, among octopuses may be context-dependent and vary in different environments and conditions.\u003c/p\u003e \u003cp\u003eThe present study showed activity significantly varied among individuals and days, which may indicate the presence of personality in octopuses (Mather and Anderson \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). Octopus personality was first suggested by Mather and Anderson (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1993\u003c/span\u003e), who found that octopus temperaments included activity, reactivity, and avoidance that resembles the temperamental dimensions described for human infants (Buss and Plomin \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1986\u003c/span\u003e), rhesus monkeys (Stevenson-Hinde et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e1980\u003c/span\u003e), and stickleback fish (Huntingford \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1976\u003c/span\u003e). Individual octopuses can consistently differ from one another in the degree of response or tendency to behave in a certain way, and related individuals are more similar than unrelated individuals in their degree and type of behaviour (Sinn et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). The individual octopuses in this experiment mostly exhibited behaviour that was consistent for each individual across multiple contexts and time, suggesting they had individual personalities (Pronk et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003e \u003cem\u003eOctopus tetricus\u003c/em\u003e is being investigated as a new fisheries target species. The present study highlighted the targeted trap fishing methods that may be a viable approach. Here, the highest capture rates came from fine-mesh crab traps, and most interactions occurred with the solid trigger trap. This study also provided a clear view of the activity pattern of \u003cem\u003eO. tetricus\u003c/em\u003e in an aquarium setting, supporting field observations of diurnal octopus activity in Eastern Australia (Godfrey-Smith and Lawrence \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Scheel et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Octopus varied significantly in their responses to introduced traps and baits, with some bold individuals being captured multiple times and accounting for the bulk of interactions. In contrast, other octopus were more timid and rarely left their dens. Relative to many other fisheries species, octopus are highly intelligent animals with complex, flexible behaviour patterns. In light of this, it is important to consider the behavioural responses and wellbeing of octopuses in their interactions with fishing gear.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis project was supported by funding from the Fisheries Research and Development Corporation (Project No. 2020-008) on behalf of the Australian Government.\u003c/p\u003e\n\u003cp\u003eConflicts of interest\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003eEthics approval\u003c/p\u003e\n\u003cp\u003eOctopus collection, experiments and maintenance of live octopuses were performed under NSW DPI permit (P01/0059(A)-4.0) and followed the recommendations of the NSW DPI Ethics Committee (ACEC REF 22/01) in collaboration with Southern Cross University ACEC.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eData/code availability\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analysed during the current study are available on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAdam A. Vrandich: conceptualisation, investigation, visualisation, methodology, analysis, writing of the original manuscript draft, and subsequent review and editing. Karina Hall: conceptualisation, investigation, visualisation, methodology, analysis, funding acquisition, research supervision, writing – review and editing. Brendan P. Kelaher: investigation, funding acquisition, research supervision, writing – review and editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAmbrose RF (1984) Food preferences, prey availability, and the diet of \u003cem\u003eOctopus bimaculatus\u003c/em\u003e Verrill. J Exp Mar Biol Ecol 77: 29-44. https://doi.org/10.1016/0022-0981(84)90049-2\u003c/li\u003e\n \u003cli\u003eAmodio P (2019) Octopus intelligence: The importance of being agnostic. 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Fish and Fisheries 19: 30-39. https://doi.org/10.1111/faf.12233\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"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":"Octopus, fisheries, animal behaviour, octopus ethics, octopus activity, Octopus tetricus","lastPublishedDoi":"10.21203/rs.3.rs-4416218/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4416218/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eOctopus fisheries are expanding globally. However, given their complex behavioural repertoires, cognitive capacities and individual personalities among octopuses, careful consideration of their interactions with and capture by fishing gears is required to inform efficient, sustainable, and ethical fisheries development. Here, the behaviour of \u003cem\u003eOctopus tetricus\u003c/em\u003e was assessed in response to different bait and trap combinations in an outdoor mesocosm experiment. Eight wild octopuses were collected, maintained in individual tanks with flow-through seawater and aeration, and monitored with a 24-h video surveillance system. Six different trap types and four different baits were presented to each octopus in various combinations during four sequential trials. Fine-mesh crab traps were the most successful in capturing octopus, accounting for 23 of the total 30 captures across all trials. Whereas solid trigger traps produced the greatest number of other interactions (e.g., octopus sitting on trap or in the entrance), averaging 43 interactions per trial, but were rarely triggered. Bait type did not influence octopus capture, trap interaction frequency, or octopus activity. Octopus were generally inactive, dedicating only 9.5% of their total time to active behaviours. Octopus activity varied with time of day, with peak activity during morning daylight (0800\u0026ndash;1200) and the lowest activity during the dark hours of the very early morning (0000\u0026ndash;0400). Additionally, capture numbers, trap interactions, and activity varied among individuals, with bolder personalities in some octopus. This natural variation among individual octopuses may lead to fishery-induced selection associated with the elevated capture frequency of bold or more active individuals.\u003c/p\u003e","manuscriptTitle":"Behavioural patterns of Octopus tetricus (Mollusca: Cephalopoda) and their responses to fisheries trap and bait combinations","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-30 20:15:53","doi":"10.21203/rs.3.rs-4416218/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revise and Resubmit","date":"2024-06-19T16:43:39+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-05-28T16:22:09+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-16T21:57:29+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-15T17:36:47+00:00","index":"","fulltext":""},{"type":"submitted","content":"Marine Biology","date":"2024-05-13T23:36:28+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":"90baf446-d269-4e46-87ba-b321eda46a74","owner":[],"postedDate":"May 30th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-10-21T16:09:49+00:00","versionOfRecord":{"articleIdentity":"rs-4416218","link":"https://doi.org/10.1007/s00227-024-04534-y","journal":{"identity":"marine-biology","isVorOnly":false,"title":"Marine Biology"},"publishedOn":"2024-10-14 15:57:14","publishedOnDateReadable":"October 14th, 2024"},"versionCreatedAt":"2024-05-30 20:15:53","video":"","vorDoi":"10.1007/s00227-024-04534-y","vorDoiUrl":"https://doi.org/10.1007/s00227-024-04534-y","workflowStages":[]},"version":"v1","identity":"rs-4416218","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4416218","identity":"rs-4416218","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}