Species dispersal through the raw water transfer invasion pathway

Species dispersal through the raw water transfer invasion pathway | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Species dispersal through the raw water transfer invasion pathway Ava Waine, Peter Robertson, Zarah Pattison This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7366251/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 13 Feb, 2026 Read the published version in Biological Invasions → Version 1 posted 5 You are reading this latest preprint version Abstract Raw water transfers (RWTs) are a globally occurring freshwater invasion pathway. Recently, the need to better understand the invasion risk posed by RWTs and develop pathway management strategies has been recognised. However, as a complex and challenging pathway to study, few direct investigations of RWTs have been carried out previously, and a detailed understanding of pathway activity is currently lacking. We therefore carried out a preliminary investigation of three separate enclosed RWTs in the northeast of England to obtain direct evidence of species dispersal. In total, viable specimens of 24 different species, including the non-native Crangonyx sp . and New Zealand mud snail ( P. antipodarum ) were dispersed, though the introduction capacity of each RWT varied substantially. This study sheds light on the role of RWTs in the secondary spread of diverse species, and demonstrates that different pathway characteristics may influence the species introduction capacity of individual RWTs. The study also highlights that given the complexity and variation inherent within the RWT pathway, risk-based approaches to pathway management may be inefficient for meeting this global management challenge. Figures Figure 1 1. Introduction Understanding and managing freshwater invasion pathways, the physical means by which species are dispersed to a non-native range, is a key aim in the field of invasive non-native species (INNS) management (Vander Zanden & Olden, 2008 ). Despite the important role of invasions pathways, a detailed understanding of viable propagule pressure, species diversity, and the mechanistic basis of translocation is often lacking for many pathways, due to a paucity of empirical investigations. Indeed, pathways can be difficult to sample directly, owing to stochastic activity and logistical challenges (García-Bethou et al. 2005). Assessments of pathway activity are typically retrospective and inferred, and proxies of introduction potential are used to estimate invasion risk (Hänfling et al. 2011 ), such as ballast water volume for the ballast water pathway. Whilst proxies are a useful and accessible means of studying invasions pathways, they may not accurately reflect real-world viable introduction effort or accurately portray which species can and cannot be dispersed by a given pathway (Drake et al. 2015 ). In England, environmental regulators have introduced requirements for stakeholders to risk assess and prioritise individual raw water transfer (RWT) schemes for pathway management (Waine et al. 2025 ). However, though a globally occurring pathway which has been linked to the secondary spread of diverse invasive taxa, few studies have directly investigated RWTs to obtain in situ evidence of dispersal (Waine et al. 2023 ). RWTs are structurally complex infrastructure systems which can include many components such as pumping stations, filters, screens, pipes, tunnels, and water supply canals; each of which may vary in size, shape and composition. Additionally, the water volume transferred, the distance covered by infrastructure and transfer frequency can also vary substantially between schemes. Knowledge of how these factors influence the introduction risk of different RWTs in isolation or in conjunction with each other is currently absent (Waine et al. 2024 ). Proxies used to estimate the invasion risk of individual schemes may therefore be unrepresentative of the true introduction effort of different RWTs. A direct investigation into three different enclosed RWT systems in Northeast England was carried out to advance our understanding of pathway activity and the introduction risks associated with different RWTs. 2. Methods 2.1 RWT selection RWT were chosen based on several criteria 1) present in the study area 2) RWTs could be accessed safely for sampling 3) water transfer was reoccurring to allow repeated sampling 4) water at the transfer outlet could be sampled just before reaching the recipient waterbody 5) transfer occurred via ‘enclosed’ infrastructure (tunnels and pipelines). This was to ensure that there were no other points of species’ entry into the RWT infrastructure via natural spread (e.g. exozoochory, wind dispersal) or the convergence of multiple watercourses. Therefore, that species sampled at the outlet must have originated from the donor waterbody. Based on this criteria, three separate RWT schemes across the Northeast of England were chosen for sampling. The selected RWTs varied in many ways including: differences in transfer infrastructure (pipe/tunnel), pipe/tunnel diameter, pipe/tunnel length, total water volume transferred, inlet waterbody type (river/reservoir), type of pumping station, filter type, the level of screening/barriers, where within the inlet waterbody the withdrawal pipe is located. 2.1.1 RWT 1 Water is conveyed from a donor reservoir to a river via a gravity mediated release which occurs through a valve at the reservoir base. Water then passages through an ~ 18 km subterranean concrete lined tunnel, 2.91 m in diameter. The tunnel exit is covered by a set of narrow iron bars approximately 15 cm apart, through which water passes before travelling down an approximately 20 m concrete spillway to the river (Fig. 1 ). 2.1.2 RWT 2 Water is transferred from a river to a reservoir via a 5 km underground steel pipeline 0.84 m in diameter. Water initially flows into a riverside pumping station through metal bars 100 cm apart, that are designed to prevent ingress of trees and large debris. Water is abstracted and passes through a finer grill which covers the sump area. Thereafter, water is mechanically pumped through a series of vortex filters, and pumped up an incline for 5 km. The pipeline terminates into a concrete basin at the recipient reservoir (Fig. 1 ). 2.1.3 RWT 3 Water is abstracted from a river via mechanical pumping, which is propelled up a steep incline via a short ( ~ < 0.5 km) subterranean 0.91 m diameter steel pipeline (Fig. 1 ). Importantly, an Environmental Fish Exclusion Screen, comprised of vertical traveling band screens and made of engineered polymer with a 2 mm aperture, is also present at the river abstraction point. These screens are installed to comply with The Eels (England and Wales) Regulations 2009 Council Regulation (EC) No 1100/2007, which requires riverine abstraction points within 30 km of coastal waters to guard against the uptake of protected fish species. Table 1 Site and infrastructure information for the three RWTs studied. RWT Inlet type Outlet type Water movement Screening Water volume (Ml/day) Transfer length Transfer infrastructure RWT 1 Reservoir River Gravity ~ 150 mm bars 20 18 km Tunnel RWT 2 River Reservoir Pumped > 50 mm bar screen 55 5 km Pipeline RWT 3 River Water treatment facility Pumped 2 mm fish exclusion screen 55 < 0.5 km Pipeline 2.2 General RWT outlet sampling methodology The outlet of each RWT was sampled on three separate occasions for 3 hours (9 hours per site in total), during August and September 2022. Mesh nets were deployed at the outlets to capture species exiting. Due to the large variation in outlet composition, accessibility constraints and difficulties in sampling large volume of turbulent and fast flowing water, the net type used had to be tailored to each RWT. A combination of Surber samplers, dredge nets and butterfly nets were used at different sites (Fig. 1 ). The mesh size of each net also varied from 65–500 um. All mesh sizes were sufficiently small to trap sediment and fine particles, and therefore all organisms of interest in this study (intact aquatic animals visible to the human eye). Whilst it would have been preferrable to use the same nets for each site for a standardised approach, the volume of water flowing through the net and the area of wetted net is more likely to influence outcomes than net dimensions per say. At intervals of 30 minutes nets were removed, checked for damage and the contents transferred into 30 x 15cm plastic trays for sorting. Intervals of 30 minutes were chosen to allow sufficient time for specimen capture, whilst minimising the potential damage from water velocity to the specimens caught in the nets. Following removal, nets were returned to the original position. The time during which nets were removed and checked did not contribute to the 3-hour sampling period. Owing to the high velocity of water movement and rapid changes in flow caused by changes in environment at outflow location, flow could not be directly measured. Flow rate through pipelines/tunnels is highly regulated, and flow within RWT infrastructure remains relatively constant and stable until the point of exit. The volume of water sampled at each site visit was therefore estimated based on knowledge (pers comms Northumbrian Water) of total water flow per day, estimations of hourly flow rate, sampling duration and the approximate proportional area of the water outlet point (ie. spillway, chamber) which was covered by nets (Table 2 ). Table 2 Estimated volume of water sampled at each site in megalitres (Ml). Site Volume sampled per visit (Ml) Total volume across 3 visits (Ml) RWT 1 0.6 1.8 RWT 2 1.35 4.05 RWT 3 0.86 2.5 2.3 Specimen processing & identification All whole or largely intact specimens were kept for identification; small fragments of organisms which were unlikely to be identifiable (such as leg segments) were discarded. All organisms were inspected on-site for viability immediately following removal from the nets – viability assessment was based on observations of movement over several minutes and/or response to touch stimuli. Organisms were then categorized as ‘viable or ‘non-viable’ and stored in a 70% ethanol solution for later identification. For each specimen an ID as specific as possible was aimed for but in some cases species-specific identification was not possible due to the loss of identifying markers/damage. These specimens were therefore identified to higher taxonomic levels, and identical specimens were grouped e.g. Simulium sp.1, Simulium sp.2 (Table 3 ). 3. Key Findings A diverse range of viable freshwater animal organisms, including fish, molluscs, crustaceans, worms, and insects were actively dispersed across all three RWTs. The specimens represented a diversity of habitats, including pelagic, benthic and substrate dwelling species. In total, 24 unique species were identified in the samples, which included two species non-native to Britain: Crangonyx sp. and the New Zealand mud snail ( P. antipodarum ). Whilst these species are considered invasive globally (Alonzo and Castro-Diez 2008; Grabowski et al. 2012 ), little is understood about their ecological impact in England, though it is likely they exert a low to moderate ecological impact in some cases (GBNNSS 2015 ; 2025 ). Undamaged plant seeds and plant fragments were also sampled, though these were not identified within the current study. Viable propagule size (VPS) per million litres, species richness and abundance differed between each RWT. RWT 1 had the largest estimated VPS (57), highest number of unique species (14), and the greatest total abundance (viable and non-viable) of specimens (146) (Table 3 , Table 4 ). The non-native shrimp Crangonyx sp. was the most abundant individual species recorded at RWT 1 (120 specimens in total); followed by the small-bodied three-spined stickleback fish Gasterosteus aculaeatus ( 6 specimens in total) andthe non-native New Zealand mud snail P. antipodarum ( 4 specimens in total). All other species were represented by 1–3 specimens. Insects were the most numerous single taxonomic group (7 species). RWT 2 had the second highest VPS (42) and was the second most species rich/abundant site. Ten species were sampled, comprising 21 individual specimens. Hydrachnidia spp. 1 was found in highest abundance (5 specimens in total) followed by P. antipodarum (4 specimens in total). All other species were represented by between 1–3 specimens. Similarly to RWT 1, insects were the most abundant taxonomic group, with five different insect species sampled at RWT 2 (Table 3 ). RWT 3 had the lowest VPS (12), species richness and abundance, with four different species present, each represented by only a single specimen. Again, insects were the most represented taxonomic group (2). Non-native Crangonyx sp. was the most sampled individual species across all sites; a total of 121 specimens from RWT 1 and 2. followed by non-native P. antipodarum with eight specimens in total from RWT 1 and 2 (Table 3 ). No individual species was found at all three sites. The only taxonomic group to be sampled at all three sites was insects. Insects were the most well represented group with 13 different species in total, which equates to over half the total number of species observed in the study (24 specimens in total). There were no clear species-specific patterns in survival relative to species/RWT, likely owing to the relatively small sample sizes. However, at each site the number of living specimens sampled was greater than the number of non-viable specimens. Table 3 Freshwater animals sampled at each raw water transfer outlet. Non-native species are highlighted in bold. Site Species name Taxon Count viable Count Non-viable RWT 1 Dixa nebulosa Insect Diptera 2 0 Dixa puberla Insect Diptera 2 0 Dolichopodidae spp. 1 Insect Diptera 1 0 Ecdyonorus dispar Insect Ephemeroptera 1 0 Simulium spp. 1 Insect Diptera 2 0 Thaumalidae spp. 1 Insect Diptera 2 0 Tipulidae spp. 1 Insect Diptera 1 0 Helobdella stagnalis Leech Rhynchobdellida 1 0 Crangonyx sp. Amphipod Amphipoda 85 35 Potamopyrgus antipodarum Mollusc Littorinimorpha 4 0 Gasterosteus aculaeatus Fish Perciformes 2 4 Rutilus rutilus Fish Cypriniformes 0 2 Ancylus fluviatalis Limpet Hygrophila 0 1 Stylodrilus heringianus Worm Lumbriculida 0 1 Total no. species 11 5 Total no. specimens 103 43 RWT 2 Orthocladiinae spp. 1 Insect Diptera 3 0 Simulium spp. 1 Insect Diptera 1 1 Simulium spp. 2 Insect Diptera 2 0 Crangonyx sp. Amphipod Amphipoda 1 0 Potamopyrgus antipodarum Mollusc Littorinimorpha 4 0 Hydrachnidia spp. 1 Water mite Trombidiformes 5 0 Gordius aquaticus Worm Gordioidea 1 0 Hydropsyche angustipennis Insect Trichoptera 0 1 Ryachophila dorsalis Insect Trichoptera 0 1 Tinoides waeneri Insect Trichoptera 0 1 Total no. species 7 4 Total no. specimens 17 4 RWT 3 Sphaernum corneum Clam 1 0 Chironomini spp. 1 Insect 1 0 Ecdyonorus dispar Insect 1 0 Asellus aquaticus Water louse 0 1 Total no. species 3 1 Total no. specimens 3 1 Table 4 Percentage of total species captured alive from each RWT and the estimated total number of viable propagules per million litres. RWT Percentage of viable specimens Viable propagules per million litres RWT 1 70.5 57 RWT 2 80.9 4.2 RWT 3 75% 1.2 4. Significance 4.1 Pathway activity This is the first study to directly assess and compare the species introduction potential of three different RWTs, and highlights the role of the pathway in dispersing a taxonomically diverse range of species. In total, viable specimens of twenty four unique species, representing a broad range of functional diversity and microhabitats, were transferred by the three RWTs, including two species non-native to Britain ( Crangonyx sp . and P. antipodarum ). As such, it is reasonable to conclude that analogous INNS may be transferred in future if present at the donor waterbodies (Rothlisberger et al. 2010 ). The majority of all whole specimens captured were viable. The traits permitting survival during the transit stage of invasion are currently poorly understood (Stasko et al. 2012). Studies tend to combine the dispersal and establishment stage of invasion in the context of trait assessments (Kolar and Lodge 2001 ) and focus predominantly on traits conducive to establishment, such as tolerance to salinity or temperature fluctuations rather than dispersal directly (Cassey et al. 2004 ). For the RWT pathway, traits conducive to the dispersal phase are likely associated with morphological hardiness and small-body size, which confers protection against the physical stresses encountered during the transfer, rather than physiochemical tolerance. The level of physiological tolerance required to survive transfer likely depends on RWT characteristics. 4.2 Pathway risk and management The variation in species richness and abundance transferred by each RWT indicates there is a difference in introduction risk/capacity for each RWT. Indeed, RWT 1 transferred a broad range of organisms including viable fish specimens, and large numbers of non-native Crangonyx sp. (85 in total), whilst RWT 3 introduced only a single specimen of 4 species in total. RWT 1 could therefore be considered to present a higher risk RWT than RWT 3. It is likely that differing physical characteristics of each RWT, in addition to ecological variation within the donor waterbodies, influenced pathway risk. Given the large variation between the three RWTs, and the differences in sampling method that was required, it is impossible to know definitively which factors influenced the observed sampling patterns. However, the results of this investigation can be used to support a preliminary insight in to the potential influence of key RWT characteristics, particularly water volume and physical barriers, on pathway introduction risk. Water volume is a widely used proxy of propagule pressure for the ballast water pathway (Wonham et al. 2005). However, this hypothesis has received little empirical assessment, particularly for freshwater species (Colautti 2005 ), and recent findings suggest that ballast sediment may in some cases be a more robust proxy for introduction potential than water release (Simard et al. 2024). Interestingly, RWT 1 transferred the least water volume (20 Ml/day) by a substantial margin, yet dispersed the largest number of species and viable propagules (approximately 57 viable propagules per million litres) compared with RWT 2 and RWT (4.1 and 1.2 respectively). That propagule size/species diversity did not increase with greater water volume suggests that water volume may be not a defining risk factor of the RWTs studied. Indeed, as the water volumes involved in all three RWTs schemes is so large, the impact of volume on transfer risk may become somewhat diluted relative to other RWT pathway characteristics. Despite being the lowest volume transfer, RWT 1 still receives 20,000,000 litres (the equivalent of eight Olympic sized swimming pools) of water per day, which is clearly sufficient to transfer a large number of species. Therefore, whilst higher water volume could theoretically increase the uptake of specimens from the source pool, is it likely that the physical constraints imposed upon specimens within these complex infrastructure systems may have a greater influence on viable propagule uptake and survival during transit. The three RWTs present a range of different obstacles to species passage. RWT 1 could be considered to have the least barriers, as water is moved by gravity through a wide tunnel, and is therefore not mechanically pumped or screened. RWT 2 was could be considered to contain a moderately high levels of barriers, as abstracted river water is filtered and pumped under pressure against gravity for 5km. This activity likely presents a significant barrier to species survival. RWT 3 was considered to have the highest level of barriers as there are 2 mm aperture exclusion screens at the river intake, filters and pumps. These preliminary findings therefore suggest that the barrier level of RWTs may exert a substantial influence on pathway introduction capacity, more so than water volume. 4.3 Difficulties in risk assessing RWTs RWTs are a complex dispersal pathway with many variables that differ between individual schemes. This creates difficulties in accurately quantifying risk factors and comparing between different RWTs. Without substantial further research into the many different RWT schemes that exist, current risk estimations are unlikely to be unreflective of real-world pathway risk. Risk-based approaches to prioritisation may therefore be unsuitable to support efficient management decisions for the large number of RWTs in England (Waine et al. 2025 ). In addition, within a risk-based decision framework, how to prioritise between RWTs with similar estimated risk levels will still remain a challenge. Given that action must be taken quickly to manage RWTs, we suggest a non risk-based approach to RWT prioritisation may be used to support decision-making. Where many interconnected RWTs are present in a region, they can acquire the properties of complex networks (Wang et al. 2023 ). Network analysis could therefore be used to determine the relative importance of individual RWTs within a wider network (Tumiran and Sivukumar, 2021). Network-based approaches may target management at key RWTs in order to strategically disrupt INNS movement across the network for maximum impact, as has been suggested for other aquatic invasion pathways (Kvistad et al. 2019 ). Though as with all approaches to INNS management, it is vital that the feasibility of management action is considered in conjunction with determinations of priority from the outset (Booy et al. 2017 ), alongside a clearly defined management aim. Declarations This work was supported by the Natural Environment Research Council (NERC) funded ONE Planet Doctoral Training Partnership [NE/S007512/1] and Northumbrian Water Limited. The authors have no relevant financial or non-financial interests to disclose.” Acknowledgments We thank members of staff from the Environment Agency, Newcastle upon Tyne, for kindly confirming the identity of specimens. References Alonso A, Castro-Díez P (2008) What explains the invading success of the aquatic mud snail Potamopyrgus antipodarum (Hydrobiidae, Mollusca)? 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Fisheries 35:121–132. https://doi.org/10.1577/1548-8446-35.3.121 Stasko AD, Patenaude T, Strecker AL, Arnott SE (2011) Portage connectivity does not predict establishment success of canoe-mediated dispersal for crustacean zooplankton. Aquatic Ecology 46:9–24. https://doi.org/10.1007/s10452-011-9378-4 Tumiran SA, Sivakumar B (2021) Community structure concept for catchment classification: A modularity density-based edge betweenness (MDEB) method. Ecological Indicators 124:107346. https://doi.org/10.1016/j.ecolind.2021.107346 Vander Zanden MJ, Olden JD (2008) A management framework for preventing the secondary spread of aquatic invasive species. Canadian Journal of Fisheries and Aquatic Sciences 65:1512–1522. https://doi.org/10.1139/f08-099 Waine A, Robertson P, Pattison Z (2024) Understanding and classifying the raw water transfer invasion pathway. Biological Invasions. https://doi.org/10.1007/s10530-024-03432-0 Waine A, Robertson P, Pattison Z (2025) Integrated management of the raw water transfer invasion pathway. Management of Biological Invasions 16(1): 227–246, https://doi.org/10.3391/mbi.2025.16.1.14 Waine A, Robertson PA, Pattison Z (2023) Raw water transfers: why a global freshwater invasion pathway has been overlooked. Hydrobiologia 851:1091-1094 https://doi.org/10.1007/s10750-023-05373-6 Wang L, He F, Zhao Y, et al (2023) Complex network-based analysis of inter-basin water transfer networks. Ecological Indicators 156:111197–111197. https://doi.org/10.1016/j.ecolind.2023.111197 Wonham MJ, Byers JE, Grosholz ED, Leung B (2013) Modeling the relationship between propagule pressure and invasion risk to inform policy and management. Ecological Applications 23:1691–1706. https://doi.org/10.1890/12-1985.1 Cite Share Download PDF Status: Published Journal Publication published 13 Feb, 2026 Read the published version in Biological Invasions → Version 1 posted Editorial decision: Major revisions 24 Sep, 2025 Reviewers agreed at journal 18 Aug, 2025 Reviewers invited by journal 17 Aug, 2025 Editor assigned by journal 14 Aug, 2025 First submitted to journal 13 Aug, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-7366251","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":501552853,"identity":"6d7a9e9e-d6e4-4777-8b78-d6d9dfe02f65","order_by":0,"name":"Ava Waine","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCElEQVRIiWNgGAWjYLCCBAYGOX4Yhw9KGxDSYizZAGFLsBGlBQgSNxwgVgt/A4/hh4c7bBg3324+JvGjpq6Ojb2B8cMPhsPGuLRIHOAxlkg8k8ZsdudYmmTPscMSbDwHmCV7GA6b4XTRAd4NEolth9nMbuSY3WZgOyDBJpHAIM3AcNgGlw75A7ybfyS2/ecxnpH/7TbDvzoJNvkHzL/xaTE4wLsNaMsBCQOJHLbbjG3MQFsY2EC24HSY4WH+bxaJbckGEjfSzH/29h2WbONJbLPsMUjH6X25423JN3+22dX3z0h+bPDjWx0/P/vhwzd+VFgbNuDSw4wpxNhARESOglEwCkbBKMAHABETUJZn1snLAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0001-8723-6101","institution":"Northumbrian Water Ltd","correspondingAuthor":true,"prefix":"","firstName":"Ava","middleName":"","lastName":"Waine","suffix":""},{"id":501552854,"identity":"c0f55c91-f340-495b-80d8-d6477d46896c","order_by":1,"name":"Peter Robertson","email":"","orcid":"","institution":"Newcastle University","correspondingAuthor":false,"prefix":"","firstName":"Peter","middleName":"","lastName":"Robertson","suffix":""},{"id":501552855,"identity":"ccdda29e-3afb-4147-a27b-fc4786b09b04","order_by":2,"name":"Zarah Pattison","email":"","orcid":"","institution":"University of Stirling","correspondingAuthor":false,"prefix":"","firstName":"Zarah","middleName":"","lastName":"Pattison","suffix":""}],"badges":[],"createdAt":"2025-08-13 15:05:52","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7366251/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7366251/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10530-026-03757-y","type":"published","date":"2026-02-13T15:57:32+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":90035155,"identity":"71906fd5-e29d-42bb-a90a-39d1634d4e79","added_by":"auto","created_at":"2025-08-27 15:44:13","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":155112,"visible":true,"origin":"","legend":"\u003cp\u003eA schematic representation of the three RWT schemes investigated and the position of sampling nets. Water flow is indicated by arrow direction.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7366251/v1/ac2d787f473678b58853b8a0.png"},{"id":102785284,"identity":"bca3a32a-919d-413d-8fac-52e3e68540aa","added_by":"auto","created_at":"2026-02-16 16:04:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":835708,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7366251/v1/f221ec47-4147-4886-8da4-dfab8afe4817.pdf"}],"financialInterests":"","formattedTitle":"Species dispersal through the raw water transfer invasion pathway","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eUnderstanding and managing freshwater invasion pathways, the physical means by which species are dispersed to a non-native range, is a key aim in the field of invasive non-native species (INNS) management (Vander Zanden \u0026amp; Olden, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eDespite the important role of invasions pathways, a detailed understanding of viable propagule pressure, species diversity, and the mechanistic basis of translocation is often lacking for many pathways, due to a paucity of empirical investigations. Indeed, pathways can be difficult to sample directly, owing to stochastic activity and logistical challenges (Garc\u0026iacute;a-Bethou et al. 2005).\u003c/p\u003e\u003cp\u003eAssessments of pathway activity are typically retrospective and inferred, and proxies of introduction potential are used to estimate invasion risk (H\u0026auml;nfling et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), such as ballast water volume for the ballast water pathway. Whilst proxies are a useful and accessible means of studying invasions pathways, they may not accurately reflect real-world viable introduction effort or accurately portray which species \u003cem\u003ecan\u003c/em\u003e and \u003cem\u003ecannot\u003c/em\u003e be dispersed by a given pathway (Drake et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn England, environmental regulators have introduced requirements for stakeholders to risk assess and prioritise individual raw water transfer (RWT) schemes for pathway management (Waine et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). However, though a globally occurring pathway which has been linked to the secondary spread of diverse invasive taxa, few studies have directly investigated RWTs to obtain \u003cem\u003ein situ\u003c/em\u003e evidence of dispersal (Waine et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eRWTs are structurally complex infrastructure systems which can include many components such as pumping stations, filters, screens, pipes, tunnels, and water supply canals; each of which may vary in size, shape and composition. Additionally, the water volume transferred, the distance covered by infrastructure and transfer frequency can also vary substantially between schemes. Knowledge of how these factors influence the introduction risk of different RWTs in isolation or in conjunction with each other is currently absent (Waine et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Proxies used to estimate the invasion risk of individual schemes may therefore be unrepresentative of the true introduction effort of different RWTs.\u003c/p\u003e\u003cp\u003eA direct investigation into three different enclosed RWT systems in Northeast England was carried out to advance our understanding of pathway activity and the introduction risks associated with different RWTs.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 RWT selection\u003c/h2\u003e\u003cp\u003eRWT were chosen based on several criteria 1) present in the study area 2) RWTs could be accessed safely for sampling 3) water transfer was reoccurring to allow repeated sampling 4) water at the transfer outlet could be sampled just before reaching the recipient waterbody 5) transfer occurred via \u0026lsquo;enclosed\u0026rsquo; infrastructure (tunnels and pipelines). This was to ensure that there were no other points of species\u0026rsquo; entry into the RWT infrastructure via natural spread (e.g. exozoochory, wind dispersal) or the convergence of multiple watercourses. Therefore, that species sampled at the outlet must have originated from the donor waterbody. Based on this criteria, three separate RWT schemes across the Northeast of England were chosen for sampling. The selected RWTs varied in many ways including: differences in transfer infrastructure (pipe/tunnel), pipe/tunnel diameter, pipe/tunnel length, total water volume transferred, inlet waterbody type (river/reservoir), type of pumping station, filter type, the level of screening/barriers, where within the inlet waterbody the withdrawal pipe is located.\u003c/p\u003e\u003cdiv id=\"Sec4\" class=\"Section3\"\u003e\u003ch2\u003e2.1.1 RWT 1\u003c/h2\u003e\u003cp\u003eWater is conveyed from a donor reservoir to a river via a gravity mediated release which occurs through a valve at the reservoir base. Water then passages through an ~\u0026thinsp;18 km subterranean concrete lined tunnel, 2.91 m in diameter. The tunnel exit is covered by a set of narrow iron bars approximately 15 cm apart, through which water passes before travelling down an approximately 20 m concrete spillway to the river (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\u003ch2\u003e2.1.2 RWT 2\u003c/h2\u003e\u003cp\u003eWater is transferred from a river to a reservoir via a 5 km underground steel pipeline 0.84 m in diameter. Water initially flows into a riverside pumping station through metal bars 100 cm apart, that are designed to prevent ingress of trees and large debris. Water is abstracted and passes through a finer grill which covers the sump area. Thereafter, water is mechanically pumped through a series of vortex filters, and pumped up an incline for 5 km. The pipeline terminates into a concrete basin at the recipient reservoir (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e2.1.3 RWT 3\u003c/h2\u003e\u003cp\u003eWater is abstracted from a river via mechanical pumping, which is propelled up a steep incline via a short (\u0026thinsp;~\u0026thinsp;\u0026lt;\u0026thinsp;0.5 km) subterranean 0.91 m diameter steel pipeline (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Importantly, an Environmental Fish Exclusion Screen, comprised of vertical traveling band screens and made of engineered polymer with a 2 mm aperture, is also present at the river abstraction point. These screens are installed to comply with The Eels (England and Wales) Regulations 2009 Council Regulation (EC) No 1100/2007, which requires riverine abstraction points within 30 km of coastal waters to guard against the uptake of protected fish species.\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\u003eSite and infrastructure information for the three RWTs studied.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\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\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInlet\u003c/p\u003e\u003cp\u003etype\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eOutlet\u003c/p\u003e\u003cp\u003etype\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eWater movement\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eScreening\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eWater volume (Ml/day)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eTransfer length\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eTransfer infrastructure\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eReservoir\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRiver\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eGravity\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e~\u0026thinsp;150 mm bars\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e18 km\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eTunnel\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRiver\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eReservoir\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePumped\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;50 mm bar screen\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e5 km\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003ePipeline\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRiver\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eWater treatment facility\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePumped\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2 mm fish exclusion screen\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.5 km\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003ePipeline\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\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.2 General RWT outlet sampling methodology\u003c/h2\u003e\u003cp\u003eThe outlet of each RWT was sampled on three separate occasions for 3 hours (9 hours per site in total), during August and September 2022. Mesh nets were deployed at the outlets to capture species exiting. Due to the large variation in outlet composition, accessibility constraints and difficulties in sampling large volume of turbulent and fast flowing water, the net type used had to be tailored to each RWT. A combination of Surber samplers, dredge nets and butterfly nets were used at different sites (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The mesh size of each net also varied from 65\u0026ndash;500 um. All mesh sizes were sufficiently small to trap sediment and fine particles, and therefore all organisms of interest in this study (intact aquatic animals visible to the human eye). Whilst it would have been preferrable to use the same nets for each site for a standardised approach, the volume of water flowing through the net and the area of wetted net is more likely to influence outcomes than net dimensions per say.\u003c/p\u003e\u003cp\u003eAt intervals of 30 minutes nets were removed, checked for damage and the contents transferred into 30 x 15cm plastic trays for sorting. Intervals of 30 minutes were chosen to allow sufficient time for specimen capture, whilst minimising the potential damage from water velocity to the specimens caught in the nets. Following removal, nets were returned to the original position. The time during which nets were removed and checked did not contribute to the 3-hour sampling period.\u003c/p\u003e\u003cp\u003eOwing to the high velocity of water movement and rapid changes in flow caused by changes in environment at outflow location, flow could not be directly measured. Flow rate through pipelines/tunnels is highly regulated, and flow within RWT infrastructure remains relatively constant and stable until the point of exit. The volume of water sampled at each site visit was therefore estimated based on knowledge (pers comms Northumbrian Water) of total water flow per day, estimations of hourly flow rate, sampling duration and the approximate proportional area of the water outlet point (ie. spillway, chamber) which was covered by nets (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\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\u003eEstimated volume of water sampled at each site in megalitres (Ml).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSite\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eVolume sampled per visit (Ml)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTotal volume across 3 visits (Ml)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.5\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\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Specimen processing \u0026amp; identification\u003c/h2\u003e\u003cp\u003eAll whole or largely intact specimens were kept for identification; small fragments of organisms which were unlikely to be identifiable (such as leg segments) were discarded. All organisms were inspected on-site for viability immediately following removal from the nets \u0026ndash; viability assessment was based on observations of movement over several minutes and/or response to touch stimuli. Organisms were then categorized as \u0026lsquo;viable or \u0026lsquo;non-viable\u0026rsquo; and stored in a 70% ethanol solution for later identification. For each specimen an ID as specific as possible was aimed for but in some cases species-specific identification was not possible due to the loss of identifying markers/damage. These specimens were therefore identified to higher taxonomic levels, and identical specimens were grouped e.g. \u003cem\u003eSimulium\u003c/em\u003e sp.1, \u003cem\u003eSimulium\u003c/em\u003e sp.2 (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Key Findings","content":"\u003cp\u003eA diverse range of viable freshwater animal organisms, including fish, molluscs, crustaceans, worms, and insects were actively dispersed across all three RWTs. The specimens represented a diversity of habitats, including pelagic, benthic and substrate dwelling species. In total, 24 unique species were identified in the samples, which included two species non-native to Britain: Crangonyx sp. and the New Zealand mud snail (\u003cem\u003eP. antipodarum\u003c/em\u003e). Whilst these species are considered invasive globally (Alonzo and Castro-Diez 2008; Grabowski et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), little is understood about their ecological impact in England, though it is likely they exert a low to moderate ecological impact in some cases (GBNNSS \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Undamaged plant seeds and plant fragments were also sampled, though these were not identified within the current study.\u003c/p\u003e\u003cp\u003eViable propagule size (VPS) per million litres, species richness and abundance differed between each RWT. RWT 1 had the largest estimated VPS (57), highest number of unique species (14), and the greatest total abundance (viable and non-viable) of specimens (146) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The non-native shrimp \u003cem\u003eCrangonyx sp.\u003c/em\u003e was the most abundant individual species recorded at RWT 1 (120 specimens in total); followed by the small-bodied three-spined stickleback fish \u003cem\u003eGasterosteus aculaeatus (\u003c/em\u003e 6 specimens in total) andthe non-native New Zealand mud snail \u003cem\u003eP. antipodarum (\u003c/em\u003e 4 specimens in total). All other species were represented by 1\u0026ndash;3 specimens. Insects were the most numerous single taxonomic group (7 species).\u003c/p\u003e\u003cp\u003eRWT 2 had the second highest VPS (42) and was the second most species rich/abundant site. Ten species were sampled, comprising 21 individual specimens. \u003cem\u003eHydrachnidia\u003c/em\u003e spp. 1 was found in highest abundance (5 specimens in total) followed by \u003cem\u003eP. antipodarum\u003c/em\u003e (4 specimens in total). All other species were represented by between 1\u0026ndash;3 specimens. Similarly to RWT 1, insects were the most abundant taxonomic group, with five different insect species sampled at RWT 2 (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eRWT 3 had the lowest VPS (12), species richness and abundance, with four different species present, each represented by only a single specimen. Again, insects were the most represented taxonomic group (2).\u003c/p\u003e\u003cp\u003eNon-native \u003cem\u003eCrangonyx\u003c/em\u003e sp. was the most sampled individual species across all sites; a total of 121 specimens from RWT 1 and 2. followed by non-native \u003cem\u003eP. antipodarum\u003c/em\u003e with eight specimens in total from RWT 1 and 2 (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eNo individual species was found at all three sites. The only taxonomic group to be sampled at all three sites was insects. Insects were the most well represented group with 13 different species in total, which equates to over half the total number of species observed in the study (24 specimens in total). There were no clear species-specific patterns in survival relative to species/RWT, likely owing to the relatively small sample sizes. However, at each site the number of living specimens sampled was greater than the number of non-viable specimens.\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\u003eFreshwater animals sampled at each raw water transfer outlet. Non-native species are highlighted in bold.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSite\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSpecies name\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTaxon\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCount\u003c/p\u003e\u003cp\u003eviable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eCount\u003c/p\u003e\u003cp\u003eNon-viable\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eRWT 1\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eDixa nebulosa\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eDiptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eDixa puberla\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eDiptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eDolichopodidae spp. 1\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eDiptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eEcdyonorus dispar\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eEphemeroptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eSimulium spp. 1\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eDiptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eThaumalidae spp. 1\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eDiptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eTipulidae spp. 1\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eDiptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eHelobdella stagnalis\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLeech\u003c/p\u003e\u003cp\u003eRhynchobdellida\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eCrangonyx sp.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAmphipod\u003c/p\u003e\u003cp\u003eAmphipoda\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003ePotamopyrgus antipodarum\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMollusc\u003c/p\u003e\u003cp\u003eLittorinimorpha\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eGasterosteus aculaeatus\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFish\u003c/p\u003e\u003cp\u003ePerciformes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eRutilus rutilus\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFish\u003c/p\u003e\u003cp\u003eCypriniformes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eAncylus fluviatalis\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLimpet\u003c/p\u003e\u003cp\u003eHygrophila\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eStylodrilus heringianus\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eWorm\u003c/p\u003e\u003cp\u003eLumbriculida\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eTotal no. species\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eTotal no. specimens\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e103\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e43\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eRWT 2\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eOrthocladiinae spp. 1\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eDiptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eSimulium spp. 1\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eDiptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eSimulium spp. 2\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eDiptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eCrangonyx sp.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAmphipod\u003c/p\u003e\u003cp\u003eAmphipoda\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003ePotamopyrgus antipodarum\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMollusc\u003c/p\u003e\u003cp\u003eLittorinimorpha\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eHydrachnidia spp. 1\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eWater mite\u003c/p\u003e\u003cp\u003eTrombidiformes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eGordius aquaticus\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eWorm\u003c/p\u003e\u003cp\u003eGordioidea\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eHydropsyche angustipennis\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eTrichoptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eRyachophila dorsalis\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eTrichoptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eTinoides waeneri\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003cp\u003eTrichoptera\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal no. species\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal no. specimens\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eSphaernum corneum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eClam\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eChironomini spp. 1\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eEcdyonorus dispar\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInsect\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eAsellus aquaticus\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eWater louse\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal no. species\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal no. specimens\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1\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=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ePercentage of total species captured alive from each RWT and the estimated total number of viable propagules per million litres.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePercentage of\u003c/p\u003e\u003cp\u003eviable specimens\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eViable propagules per\u003c/p\u003e\u003cp\u003emillion litres\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e70.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e57\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e80.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRWT 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e75%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"4. Significance","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Pathway activity\u003c/h2\u003e\u003cp\u003eThis is the first study to directly assess and compare the species introduction potential of three different RWTs, and highlights the role of the pathway in dispersing a taxonomically diverse range of species. In total, viable specimens of twenty four unique species, representing a broad range of functional diversity and microhabitats, were transferred by the three RWTs, including two species non-native to Britain (\u003cem\u003eCrangonyx sp\u003c/em\u003e. and \u003cem\u003eP. antipodarum\u003c/em\u003e). As such, it is reasonable to conclude that analogous INNS may be transferred in future if present at the donor waterbodies (Rothlisberger et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe majority of all whole specimens captured were viable. The traits permitting survival during the transit stage of invasion are currently poorly understood (Stasko et al. 2012). Studies tend to combine the dispersal and establishment stage of invasion in the context of trait assessments (Kolar and Lodge \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) and focus predominantly on traits conducive to establishment, such as tolerance to salinity or temperature fluctuations rather than dispersal directly (Cassey et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). For the RWT pathway, traits conducive to the dispersal phase are likely associated with morphological hardiness and small-body size, which confers protection against the physical stresses encountered during the transfer, rather than physiochemical tolerance. The level of physiological tolerance required to survive transfer likely depends on RWT characteristics.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e4.2 \u003cem\u003ePathway risk and management\u003c/em\u003e\u003c/h2\u003e\u003cp\u003eThe variation in species richness and abundance transferred by each RWT indicates there is a difference in introduction risk/capacity for each RWT. Indeed, RWT 1 transferred a broad range of organisms including viable fish specimens, and large numbers of non-native Crangonyx sp. (85 in total), whilst RWT 3 introduced only a single specimen of 4 species in total. RWT 1 could therefore be considered to present a higher risk RWT than RWT 3.\u003c/p\u003e\u003cp\u003eIt is likely that differing physical characteristics of each RWT, in addition to ecological variation within the donor waterbodies, influenced pathway risk. Given the large variation between the three RWTs, and the differences in sampling method that was required, it is impossible to know definitively which factors influenced the observed sampling patterns. However, the results of this investigation can be used to support a preliminary insight in to the potential influence of key RWT characteristics, particularly water volume and physical barriers, on pathway introduction risk.\u003c/p\u003e\u003cp\u003eWater volume is a widely used proxy of propagule pressure for the ballast water pathway (Wonham et al. 2005). However, this hypothesis has received little empirical assessment, particularly for freshwater species (Colautti \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2005\u003c/span\u003e), and recent findings suggest that ballast sediment may in some cases be a more robust proxy for introduction potential than water release (Simard et al. 2024). Interestingly, RWT 1 transferred the least water volume (20 Ml/day) by a substantial margin, yet dispersed the largest number of species and viable propagules (approximately 57 viable propagules per million litres) compared with RWT 2 and RWT (4.1 and 1.2 respectively).\u003c/p\u003e\u003cp\u003eThat propagule size/species diversity did not increase with greater water volume suggests that water volume may be not a defining risk factor of the RWTs studied. Indeed, as the water volumes involved in all three RWTs schemes is so large, the impact of volume on transfer risk may become somewhat diluted relative to other RWT pathway characteristics. Despite being the lowest volume transfer, RWT 1 still receives 20,000,000 litres (the equivalent of eight Olympic sized swimming pools) of water per day, which is clearly sufficient to transfer a large number of species. Therefore, whilst higher water volume could theoretically increase the uptake of specimens from the source pool, is it likely that the physical constraints imposed upon specimens within these complex infrastructure systems may have a greater influence on \u003cem\u003eviable\u003c/em\u003e propagule uptake and survival during transit.\u003c/p\u003e\u003cp\u003eThe three RWTs present a range of different obstacles to species passage. RWT 1 could be considered to have the least barriers, as water is moved by gravity through a wide tunnel, and is therefore not mechanically pumped or screened. RWT 2 was could be considered to contain a moderately high levels of barriers, as abstracted river water is filtered and pumped under pressure against gravity for 5km. This activity likely presents a significant barrier to species survival. RWT 3 was considered to have the highest level of barriers as there are 2 mm aperture exclusion screens at the river intake, filters and pumps. These preliminary findings therefore suggest that the barrier level of RWTs may exert a substantial influence on pathway introduction capacity, more so than water volume.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e4.3 Difficulties in risk assessing RWTs\u003c/h2\u003e\u003cp\u003eRWTs are a complex dispersal pathway with many variables that differ between individual schemes. This creates difficulties in accurately quantifying risk factors and comparing between different RWTs. Without substantial further research into the many different RWT schemes that exist, current risk estimations are unlikely to be unreflective of real-world pathway risk. Risk-based approaches to prioritisation may therefore be unsuitable to support efficient management decisions for the large number of RWTs in England (Waine et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). In addition, within a risk-based decision framework, how to prioritise between RWTs with similar estimated risk levels will still remain a challenge.\u003c/p\u003e\u003cp\u003eGiven that action must be taken quickly to manage RWTs, we suggest a non risk-based approach to RWT prioritisation may be used to support decision-making. Where many interconnected RWTs are present in a region, they can acquire the properties of complex networks (Wang et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Network analysis could therefore be used to determine the relative importance of individual RWTs within a wider network (Tumiran and Sivukumar, 2021). Network-based approaches may target management at key RWTs in order to strategically disrupt INNS movement across the network for maximum impact, as has been suggested for other aquatic invasion pathways (Kvistad et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Though as with all approaches to INNS management, it is vital that the feasibility of management action is considered in conjunction with determinations of priority from the outset (Booy et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), alongside a clearly defined management aim.\u003c/p\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003eThis work was supported by the Natural Environment Research Council (NERC) funded ONE Planet Doctoral Training Partnership [NE/S007512/1] and Northumbrian Water Limited. The authors have no relevant financial or non-financial interests to disclose.\u0026rdquo;\u003c/p\u003e\n\u003cp\u003eAcknowledgments\u003c/p\u003e\n\u003cp\u003eWe thank members of staff from the Environment Agency, Newcastle upon Tyne, for kindly confirming the identity of specimens.\u0026nbsp;\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAlonso A, Castro-D\u0026iacute;ez P (2008) What explains the invading success of the aquatic mud snail Potamopyrgus antipodarum (Hydrobiidae, Mollusca)? Hydrobiologia 614:107\u0026ndash;116. https://doi.org/10.1007/s10750-008-9529-3\u003c/li\u003e\n\u003cli\u003eBooy O, Mill AC, Roy HE, et al (2017) Risk management to prioritise the eradication of new and emerging invasive non-native species. Biological Invasions 19:2401\u0026ndash;2417. https://doi.org/10.1007/s10530-017-1451-z\u003c/li\u003e\n\u003cli\u003eCassey P, Blackburn TM, Jones KE, Lockwood JL (2004) Mistakes in the analysis of exotic species establishment: source pool designation and correlates of introduction success among parrots (Aves: Psittaciformes) of the world. Journal of Biogeography 31:277\u0026ndash;284. https://doi.org/10.1046/j.0305-0270.2003.00979.x\u003c/li\u003e\n\u003cli\u003eColautti RI (2005) Are characteristics of introduced salmonid fishes biased by propagule pressure? Canadian Journal of Fisheries and Aquatic Sciences 62:950\u0026ndash;959. https://doi.org/10.1139/f05-002\u003c/li\u003e\n\u003cli\u003eDrake DM, Casas-Monroy O, Koops MA, Bailey SA (2015) Propagule pressure in the presence of uncertainty: extending the utility of proxy variables with hierarchical models. Methods in Ecology and Evolution 6:1363\u0026ndash;1371. https://doi.org/10.1111/2041-210x.12429\u003c/li\u003e\n\u003cli\u003eGarc\u0026iacute;a-Berthou E, Alcaraz C, Pou-Rovira Q, et al (2005) Introduction pathways and establishment rates of invasive aquatic species in Europe. Canadian Journal of Fisheries and Aquatic Sciences 62:453\u0026ndash;463. https://doi.org/10.1139/f05-017\u003c/li\u003e\n\u003cli\u003eGBNNSS (2015) GB non-native organism risk assessment scheme Crangonyx. In: Nonnativespecies.org https://www.nonnativespecies.org/search?query=crangonyx/risk%20assessment. Accessed 6 Aug 2025\u003c/li\u003e\n\u003cli\u003eGBNNSS (2025) GB NON-NATIVE ORGANISM RISK ASSESSMENT SCHEME P. antipodarum. In: Nonnativespecies.org. https://www.nonnativespecies.org/search?query=potamopyrgus/riskassessment. Accessed 6 Aug 2025\u003c/li\u003e\n\u003cli\u003eGrabowski M, Rachalewski M, Banha F, Anastacio P (2012) Crangonyx pseudogracilis Bousfield, 1958 \u0026ndash; the first alien amphipod crustacean in freshwaters of Iberian Peninsula (Portugal). Knowledge and Management of Aquatic Ecosystems 11. https://doi.org/10.1051/kmae/2012005\u003c/li\u003e\n\u003cli\u003eH\u0026auml;nfling B, Edwards F, Gherardi F (2011) Invasive alien Crustacea: dispersal, establishment, impact and control. BioControl 56:573\u0026ndash;595. https://doi.org/10.1007/s10526-011-9380-8\u003c/li\u003e\n\u003cli\u003eKolar CS, Lodge DM (2001) Progress in invasion biology: predicting invaders. 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Management of Biological Invasions 16(1): 227\u0026ndash;246, https://doi.org/10.3391/mbi.2025.16.1.14\u003c/li\u003e\n\u003cli\u003eWaine A, Robertson PA, Pattison Z (2023) Raw water transfers: why a global freshwater invasion pathway has been overlooked. \u003cem\u003eHydrobiologia \u003c/em\u003e851:1091-1094 https://doi.org/10.1007/s10750-023-05373-6\u003c/li\u003e\n\u003cli\u003eWang L, He F, Zhao Y, et al (2023) Complex network-based analysis of inter-basin water transfer networks. Ecological Indicators 156:111197\u0026ndash;111197. https://doi.org/10.1016/j.ecolind.2023.111197\u003c/li\u003e\n\u003cli\u003eWonham MJ, Byers JE, Grosholz ED, Leung B (2013) Modeling the relationship between propagule pressure and invasion risk to inform policy and management. Ecological Applications 23:1691\u0026ndash;1706. https://doi.org/10.1890/12-1985.1\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":"biological-invasions","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"binv","sideBox":"Learn more about [Biological Invasions](https://www.springer.com/journal/10530)","snPcode":"10530","submissionUrl":"https://submission.nature.com/new-submission/10530/3","title":"Biological Invasions","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7366251/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7366251/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRaw water transfers (RWTs) are a globally occurring freshwater invasion pathway. Recently, the need to better understand the invasion risk posed by RWTs and develop pathway management strategies has been recognised. However, as a complex and challenging pathway to study, few direct investigations of RWTs have been carried out previously, and a detailed understanding of pathway activity is currently lacking. We therefore carried out a preliminary investigation of three separate enclosed RWTs in the northeast of England to obtain direct evidence of species dispersal. In total, viable specimens of 24 different species, including the non-native \u003cem\u003eCrangonyx sp\u003c/em\u003e. and New Zealand mud snail (\u003cem\u003eP. antipodarum\u003c/em\u003e) were dispersed, though the introduction capacity of each RWT varied substantially. This study sheds light on the role of RWTs in the secondary spread of diverse species, and demonstrates that different pathway characteristics may influence the species introduction capacity of individual RWTs. The study also highlights that given the complexity and variation inherent within the RWT pathway, risk-based approaches to pathway management may be inefficient for meeting this global management challenge.\u003c/p\u003e","manuscriptTitle":"Species dispersal through the raw water transfer invasion pathway","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-27 15:44:09","doi":"10.21203/rs.3.rs-7366251/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revisions","date":"2025-09-24T15:29:45+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-08-18T08:09:07+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-17T19:36:18+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-14T10:23:07+00:00","index":"","fulltext":""},{"type":"submitted","content":"Biological Invasions","date":"2025-08-13T11:05:12+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"biological-invasions","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"binv","sideBox":"Learn more about [Biological Invasions](https://www.springer.com/journal/10530)","snPcode":"10530","submissionUrl":"https://submission.nature.com/new-submission/10530/3","title":"Biological Invasions","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ede7696e-95bd-46fd-a183-38510ecd634c","owner":[],"postedDate":"August 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-16T16:01:38+00:00","versionOfRecord":{"articleIdentity":"rs-7366251","link":"https://doi.org/10.1007/s10530-026-03757-y","journal":{"identity":"biological-invasions","isVorOnly":false,"title":"Biological Invasions"},"publishedOn":"2026-02-13 15:57:32","publishedOnDateReadable":"February 13th, 2026"},"versionCreatedAt":"2025-08-27 15:44:09","video":"","vorDoi":"10.1007/s10530-026-03757-y","vorDoiUrl":"https://doi.org/10.1007/s10530-026-03757-y","workflowStages":[]},"version":"v1","identity":"rs-7366251","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7366251","identity":"rs-7366251","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}