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Crawford RMB, Gee EM, Dupont DWE, Hicks BJ, Franklin PA. High water temperature significantly influences swimming performance of New Zealand migratory species. CONSERVATION PHYSIOLOGY 2024; 12:coae047. [PMID: 39086758 PMCID: PMC11289306 DOI: 10.1093/conphys/coae047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 04/25/2024] [Accepted: 07/07/2024] [Indexed: 08/02/2024]
Abstract
Anthropogenic structures in freshwater systems pose a significant threat by fragmenting habitats. Effective fish passage solutions must consider how environmental changes introduce variability into swimming performance. As temperature is considered the most important external factor influencing fish physiology, it is especially important to consider its effects on fish swimming performance. Even minor alterations in water properties, such as temperature and velocity, can profoundly affect fish metabolic demands, foraging behaviours, fitness and, consequently, swimming performance and passage success. In this study, we investigated the impact of varying water temperatures on the critical swimming speeds of four migratory New Zealand species. Our findings revealed a significant reduction in critical swimming speeds at higher water temperatures (26°C) compared to lower ones (8 and 15°C) for three out of four species (Galaxias maculatus, Galaxias brevipinnis and Gobiomorphus cotidianus). In contrast, Galaxias fasciatus exhibited no significant temperature-related changes in swimming performance, suggesting species-specific responses to temperature. The cold temperature treatment did not impact swimming performance for any of the studied species. As high water temperatures significantly reduce fish swimming performance, it is important to ensure that fish passage solutions are designed to accommodate a range of temperature changes, including spatial and temporal changes, ranging from diel to decadal fluctuations. Our research underscores the importance of incorporating temperature effects into fish passage models for habitat restoration, connectivity initiatives, and freshwater fish conservation. The influence of temperature on fish swimming performance can alter migration patterns and population dynamics, highlighting the need for adaptive conservation strategies. To ensure the resilience of freshwater ecosystems it is important to account for the impact of temperature on fish swimming performance, particularly in the context of a changing climate.
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Affiliation(s)
- Rachel M B Crawford
- School of Science, Environmental Research Institute, The University of Waikato, Room E.2.20, E Block, Gate 8, Hillcrest Road, Hamilton, 3216, New Zealand
- National Institute of Water and Atmospheric Research, Gate 10, Silverdale Road, Hillcrest, Hamilton, 3216, New Zealand
| | - Eleanor M Gee
- National Institute of Water and Atmospheric Research, Gate 10, Silverdale Road, Hillcrest, Hamilton, 3216, New Zealand
- Waikato Regional Council, 160 Ward Street, Hamilton Central, Hamilton, 3204New Zealand
| | - Deborah W E Dupont
- National Institute of Water and Atmospheric Research, Gate 10, Silverdale Road, Hillcrest, Hamilton, 3216, New Zealand
| | - Brendan J Hicks
- School of Science, Environmental Research Institute, The University of Waikato, Room E.2.20, E Block, Gate 8, Hillcrest Road, Hamilton, 3216, New Zealand
- Morphum Environmental Ltd, 65 Victoria Street, Hamilton, 3204New Zealand
| | - Paul A Franklin
- National Institute of Water and Atmospheric Research, Gate 10, Silverdale Road, Hillcrest, Hamilton, 3216, New Zealand
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Colborne S, Peiman KS, Birnie-Gauvin K, Larsen MH, Aarestrup K, Cooke SJ. Effects of pre-winter cortisol exposure on condition, diet, and morphology of wild juvenile brown trout (Salmo trutta). JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2024; 341:282-292. [PMID: 38238913 DOI: 10.1002/jez.2781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2023] [Revised: 01/03/2024] [Accepted: 01/04/2024] [Indexed: 02/27/2024]
Abstract
Winter is an energetically challenging period for many animals in temperate regions because of the relatively harsh environmental conditions and reduction in food availability during this season. Moreover, stressors experienced by individuals in the fall can affect their subsequent foraging strategy and energy stores after exposure has ended, referred to as carryover effects. We used exogenous cortisol manipulation of wild juvenile brown trout (Salmo trutta) in the fall to simulate a physiological stress response and then investigated short-term (2 weeks) and long-term (4 months) effects on condition metrics (hepatosomatic index and water muscle content), diet (stomach contents and stable isotopes), and morphology during growth in freshwater. We revealed some short-term impacts, likely due to handling stress, and long-term (seasonal) changes in diet, likely reflecting prey availability. Unfortunately, we had very few recaptures of cortisol-treated fish at long-term sampling, limiting detailed analysis about cortisol effects at that time point. Nonetheless, the fish that were sampled showed elevated stable isotopes, suggestive of a cortisol effect long after exposure. This is one of few studies to investigate whether cortisol influences foraging and morphology during juvenile growth, thus extending the knowledge of proximate mechanisms influencing ecologically-relevant phenotypes.
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Affiliation(s)
- Scott Colborne
- Department of Fisheries and Wildlife, Quantitative Fisheries Center, Michigan State University, East Lansing, Michigan, USA
- Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, Canada
| | - Kathryn S Peiman
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Institute of Environmental and Interdisciplinary Science, Carleton University, Ottawa, Ontario, Canada
| | - Kim Birnie-Gauvin
- Section for Freshwater Fisheries and Ecology, National Institute for Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark
| | - Martin H Larsen
- Section for Freshwater Fisheries and Ecology, National Institute for Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark
| | - Kim Aarestrup
- Section for Freshwater Fisheries and Ecology, National Institute for Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark
| | - Steven J Cooke
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Institute of Environmental and Interdisciplinary Science, Carleton University, Ottawa, Ontario, Canada
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Branco P, Mascarenhas AM, Duarte G, Romão F, Quaresma A, Amaral SD, Ferreira MT, Pinheiro AN, Santos JM. Vertical Slot Fishways: Incremental Knowledge to Define the Best Solution. BIOLOGY 2023; 12:1431. [PMID: 37998030 PMCID: PMC10669019 DOI: 10.3390/biology12111431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Revised: 11/03/2023] [Accepted: 11/10/2023] [Indexed: 11/25/2023]
Abstract
River artificial fragmentation is arguably the most imperilling threat for freshwater-dependent fish species. Fish need to be able to freely move along river networks as not only spawning grounds but also refuge and feeding areas may be spatially and temporally separated. This incapacity of free displacement may result in genetic depletion of some populations, density reduction and even community changes, which may in turn affect how meta-community balances are regulated, potentially resulting in functional resilience reduction and ecosystem processes' malfunction. Fishways are the most common and widely used method to improve connectivity for fish species. These structures allow fish to negotiate full barriers, thus reducing their connectivity impairment. Among all technical fishway types, vertical slot fishways (VSF) are considered to be the best solution, as they remain operational even with fluctuating water discharges and allow fish to negotiate each cross-wall at their desired depth. In the present study, we collected both published and original data on fish experiments within VSF, to address two questions, (1) What variables affect fish passage during experimental fishway studies? and (2) What is the best VSF configuration? We used Bayesian Generalized Mixed Models accounting for random effects of non-controlled factors, limiting inherent data dependencies, that may influence the model outcome. Results highlight that fish size, regardless of the species, is a good predictor of fishway negotiation success. Generally, multiple slot fishways with one orifice proved to be the best solution. Future work should be focused on small-sized fish to further improve the design of holistic fishways.
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Affiliation(s)
- Paulo Branco
- Forest Research Centre, Associate Laboratory TERRA, School of Agriculture, University of Lisbon, 1349-017 Lisbon, Portugal; (A.M.M.); (G.D.); (S.D.A.); (M.T.F.); (J.M.S.)
| | - Ana Margarida Mascarenhas
- Forest Research Centre, Associate Laboratory TERRA, School of Agriculture, University of Lisbon, 1349-017 Lisbon, Portugal; (A.M.M.); (G.D.); (S.D.A.); (M.T.F.); (J.M.S.)
| | - Gonçalo Duarte
- Forest Research Centre, Associate Laboratory TERRA, School of Agriculture, University of Lisbon, 1349-017 Lisbon, Portugal; (A.M.M.); (G.D.); (S.D.A.); (M.T.F.); (J.M.S.)
| | - Filipe Romão
- Civil Engineering for Research and Innovation for Sustainability, Instituto Superior Técnico, University of Lisbon, 1049-001 Lisbon, Portugal; (F.R.); (A.Q.); (A.N.P.)
| | - Ana Quaresma
- Civil Engineering for Research and Innovation for Sustainability, Instituto Superior Técnico, University of Lisbon, 1049-001 Lisbon, Portugal; (F.R.); (A.Q.); (A.N.P.)
| | - Susana Dias Amaral
- Forest Research Centre, Associate Laboratory TERRA, School of Agriculture, University of Lisbon, 1349-017 Lisbon, Portugal; (A.M.M.); (G.D.); (S.D.A.); (M.T.F.); (J.M.S.)
| | - Maria Teresa Ferreira
- Forest Research Centre, Associate Laboratory TERRA, School of Agriculture, University of Lisbon, 1349-017 Lisbon, Portugal; (A.M.M.); (G.D.); (S.D.A.); (M.T.F.); (J.M.S.)
| | - António N. Pinheiro
- Civil Engineering for Research and Innovation for Sustainability, Instituto Superior Técnico, University of Lisbon, 1049-001 Lisbon, Portugal; (F.R.); (A.Q.); (A.N.P.)
| | - José Maria Santos
- Forest Research Centre, Associate Laboratory TERRA, School of Agriculture, University of Lisbon, 1349-017 Lisbon, Portugal; (A.M.M.); (G.D.); (S.D.A.); (M.T.F.); (J.M.S.)
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Parasiewicz P, Belka K, Łapińska M, Ławniczak K, Prus P, Adamczyk M, Buras P, Szlakowski J, Kaczkowski Z, Krauze K, O'Keeffe J, Suska K, Ligięza J, Melcher A, O'Hanley J, Birnie-Gauvin K, Aarestrup K, Jones PE, Jones J, Garcia de Leaniz C, Tummers JS, Consuegra S, Kemp P, Schwedhelm H, Popek Z, Segura G, Vallesi S, Zalewski M, Wiśniewolski W. Over 200,000 kilometers of free-flowing river habitat in Europe is altered due to impoundments. Nat Commun 2023; 14:6289. [PMID: 37813852 PMCID: PMC10562483 DOI: 10.1038/s41467-023-40922-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 08/03/2023] [Indexed: 10/11/2023] Open
Abstract
European rivers are disconnected by more than one million man-made barriers that physically limit aquatic species migration and contribute to modification of freshwater habitats. Here, a Conceptual Habitat Alteration Model for Ponding is developed to aid in evaluating the effects of impoundments on fish habitats. Fish communities present in rivers with low human impact and their broad environmental settings enable classification of European rivers into 15 macrohabitat types. These classifications, together with the estimated fish sensitivity to alteration of their habitat are used for assessing the impacts of six main barrier types (dams, weirs, sluices, culverts, fords, and ramps). Our results indicate that over 200,000 km or 10% of previously free-flowing river habitat has been altered due to impoundments. Although they appear less frequently, dams, weirs and sluices cause much more habitat alteration than the other types. Their impact is regionally diverse, which is a function of barrier height, type and density, as well as biogeographical location. This work allows us to foresee what potential environmental gain or loss can be expected with planned barrier management actions in rivers, and to prioritize management actions.
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Affiliation(s)
| | - Kamila Belka
- National Inland Fisheries Research Institute, Olsztyn, Poland.
- European Regional Centre for Ecohydrology of the Polish Academy of Sciences, Łódź, Poland.
| | - Małgorzata Łapińska
- European Regional Centre for Ecohydrology of the Polish Academy of Sciences, Łódź, Poland
- University of Lodz, Łódź, Poland
| | - Karol Ławniczak
- European Regional Centre for Ecohydrology of the Polish Academy of Sciences, Łódź, Poland
- University of Lodz, Łódź, Poland
| | - Paweł Prus
- National Inland Fisheries Research Institute, Olsztyn, Poland
| | | | - Paweł Buras
- National Inland Fisheries Research Institute, Olsztyn, Poland
| | | | - Zbigniew Kaczkowski
- European Regional Centre for Ecohydrology of the Polish Academy of Sciences, Łódź, Poland
- University of Lodz, Łódź, Poland
| | - Kinga Krauze
- European Regional Centre for Ecohydrology of the Polish Academy of Sciences, Łódź, Poland
| | - Joanna O'Keeffe
- National Inland Fisheries Research Institute, Olsztyn, Poland
| | - Katarzyna Suska
- National Inland Fisheries Research Institute, Olsztyn, Poland
| | - Janusz Ligięza
- National Inland Fisheries Research Institute, Olsztyn, Poland
| | - Andreas Melcher
- University of Natural Resources and Life Sciences, Vienna, Austria
| | | | | | | | | | | | | | | | | | - Paul Kemp
- University of Southampton, Southampton, UK
| | | | | | | | | | - Maciej Zalewski
- European Regional Centre for Ecohydrology of the Polish Academy of Sciences, Łódź, Poland
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Consuegra S, O'Rorke R, Rodriguez-Barreto D, Fernandez S, Jones J, Garcia de Leaniz C. Impacts of large and small barriers on fish assemblage composition assessed using environmental DNA metabarcoding. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 790:148054. [PMID: 34111787 DOI: 10.1016/j.scitotenv.2021.148054] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 05/24/2021] [Accepted: 05/24/2021] [Indexed: 06/12/2023]
Abstract
River fragmentation caused by instream barriers is a leading cause of biodiversity loss, particularly for freshwater migratory fish, the vertebrate group that has suffered the steepest decline. However, most studies have tended to focus on the impacts of large dams on only a few taxa. We estimated the cumulative impact of both large and small barriers on fish species richness and relative abundance along an altitudinal gradient in the main stem of the River Allier (France). Using eDNA metabarcoding, we identified 24 fish zero-radius operational taxonomic units (zOTUs), corresponding to 26 species distributed along the main stem of the river. Elevation explained the greatest amount of variation in fish distribution, together with average flow, barrier density and its interaction with cumulative barrier height. Based on eDNA, the largest discontinuity in species richness was not related to the location of Poutès, the largest dam in the system, but located downstream from it. Our results indicate that, in addition to the more obvious effects of large dams on migratory fish such as the Atlantic salmon, the cumulative effects of small barriers can have widespread impacts on fish species richness and relative abundance, which should not be overlooked. We suggest that, as for other fragmented rivers, acting on numerous small barriers might bring about greater benefits in fish species richness than focusing only on the largest dams.
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Affiliation(s)
- Sofia Consuegra
- Department of Biosciences, 2, Swansea University, Swansea SA2 8PP, United Kingdom.
| | - Richard O'Rorke
- Department of Biosciences, 2, Swansea University, Swansea SA2 8PP, United Kingdom
| | | | - Sara Fernandez
- University of Oviedo, Department of Functional Biology, 33071 Oviedo, Spain
| | - Joshua Jones
- Department of Biosciences, 2, Swansea University, Swansea SA2 8PP, United Kingdom
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Williams HJ, Shipley JR, Rutz C, Wikelski M, Wilkes M, Hawkes LA. Future trends in measuring physiology in free-living animals. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200230. [PMID: 34176330 PMCID: PMC8237165 DOI: 10.1098/rstb.2020.0230] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/18/2021] [Indexed: 02/07/2023] Open
Abstract
Thus far, ecophysiology research has predominantly been conducted within controlled laboratory-based environments, owing to a mismatch between the recording technologies available for physiological monitoring in wild animals and the suite of behaviours and environments they need to withstand, without unduly affecting subjects. While it is possible to record some physiological variables for free-living animals using animal-attached logging devices, including inertial-measurement, heart-rate and temperature loggers, the field is still in its infancy. In this opinion piece, we review the most important future research directions for advancing the field of 'physiologging' in wild animals, including the technological development that we anticipate will be required, and the fiscal and ethical challenges that must be overcome. Non-invasive, multi-sensor miniature devices are ubiquitous in the world of human health and fitness monitoring, creating invaluable opportunities for animal and human physiologging to drive synergistic advances. We argue that by capitalizing on the research efforts and advancements made in the development of human wearables, it will be possible to design the non-invasive loggers needed by ecophysiologists to collect accurate physiological data from free-ranging animals ethically and with an absolute minimum of impact. In turn, findings have the capacity to foster transformative advances in human health monitoring. Thus, we invite biomedical engineers and researchers to collaborate with the animal-tagging community to drive forward the advancements necessary to realize the full potential of both fields. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.
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Affiliation(s)
- H. J. Williams
- Department of Migration, Max Planck Institute of Animal Behavior, 78315 Radolfzell, Germany
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78464, Konstanz, Germany
| | - J. Ryan Shipley
- Department of Migration, Max Planck Institute of Animal Behavior, 78315 Radolfzell, Germany
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78464, Konstanz, Germany
| | - C. Rutz
- Centre for Biological Diversity, School of Biology, University of St Andrews, St Andrews KY16 9TH, UK
| | - M. Wikelski
- Department of Migration, Max Planck Institute of Animal Behavior, 78315 Radolfzell, Germany
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78464, Konstanz, Germany
- Centre for the Advanced Study of Collective Behaviour, University of Konstanz, 78457 Konstanz, Germany
| | - M. Wilkes
- Extreme Environments Research Group, University of Portsmouth, Spinnaker Building, Cambridge Road, Portsmouth PO1 2EF, UK
| | - L. A. Hawkes
- Hatherly Laboratories, University of Exeter, College of Life and Environmental Sciences, Exeter EX4 4PS, UK
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Lin L, Deng W, Huang X, Liu Y, Huang L, Kang B. How fish traits and functional diversity respond to environmental changes and species invasion in the largest river in Southeastern China. PeerJ 2021; 9:e11824. [PMID: 34386304 PMCID: PMC8312501 DOI: 10.7717/peerj.11824] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 06/30/2021] [Indexed: 11/20/2022] Open
Abstract
Background Freshwater fish populations are facing multiple stressors, including climate change, species invasion, and anthropogenic interference. Temporal studies of fish functional diversity and community assembly rules based on trait-environment relationships provide insights into fish community structure in riverine ecosystems. Methods Fish samples were collected in 2015 in the Min River, the largest freshwater riverine system in Southeastern China. Fish functional diversity was compared with the background investigation in 1979. Changes in functional richness, functional evenness, functional divergence, and functional beta diversity were analyzed. Relationships between functional diversity and environmental factors were modeled by random forest regression. Correlations between fish functional traits and environmental factors were detected by fourth-corner combined with RLQ analysis. Results Functional richness was significantly reduced in 2015 compared with 1979. Functional beta diversity in 2015 was significantly higher than that in 1979, with functional nestedness being the driving component. Reduction of functional richness and domination of functional nestedness is associated with species loss. Trait convergence was the dominant mechanism driving the temporal changes of functional diversity. Precipitation, temperature, species invasion, and human population were the most significant factors driving fish functional diversity. Higher precipitation, higher temperature, and presence of invasive species were significantly associated with higher swimming factor and higher relative eye diameter, while the opposite environmental conditions were significantly associated with higher pectoral fin length and eurytopic water flow preference. Conclusions Environmental filtering is the dominant temporal assembly mechanism shaping fish community structure. This work contributes to the understanding of temporal freshwater fish community assembly and the associations between fish functional structure and local environmental conditions, which will be informative for future freshwater fish conservation.
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Affiliation(s)
- Li Lin
- College of Fisheries, Ocean University of China, Qingdao, Shandong, China
| | - Weide Deng
- Henry Fok College of Biology and Agriculture, Shaoguan University, Shaoguan, Guangdong, China.,Department of Oceanography, National Sun Yat-Sen University, Kaohsiung, Taiwan, China
| | - Xiaoxia Huang
- Key Laboratory of Atmospheric Environment and Processes in the Boundary Layer Over the Low-Latitude Plateau Region, School of Earth Science, Yunnan University, Kunming, Yunnan, China
| | - Yang Liu
- College of Fisheries, Ocean University of China, Qingdao, Shandong, China
| | - Liangliang Huang
- College of Environmental Science and Engineering, Guilin University of Technology, Guilin, Guangxi, China
| | - Bin Kang
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao, Shandong, China
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Jones PE, Champneys T, Vevers J, Börger L, Svendsen JC, Consuegra S, Jones J, Garcia de Leaniz C. Selective effects of small barriers on river‐resident fish. J Appl Ecol 2021. [DOI: 10.1111/1365-2664.13875] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Peter E. Jones
- Centre for Sustainable Aquatic Research Department of Biosciences College of Science Swansea University Swansea UK
| | - Toby Champneys
- Centre for Sustainable Aquatic Research Department of Biosciences College of Science Swansea University Swansea UK
| | - Jessica Vevers
- Centre for Sustainable Aquatic Research Department of Biosciences College of Science Swansea University Swansea UK
| | - Luca Börger
- Centre for Sustainable Aquatic Research Department of Biosciences College of Science Swansea University Swansea UK
| | - Jon C. Svendsen
- National Institute of Aquatic Resources (DTU‐Aqua)Technical University of Denmark Lyngby Denmark
| | - Sofia Consuegra
- Centre for Sustainable Aquatic Research Department of Biosciences College of Science Swansea University Swansea UK
| | - Joshua Jones
- Centre for Sustainable Aquatic Research Department of Biosciences College of Science Swansea University Swansea UK
| | - Carlos Garcia de Leaniz
- Centre for Sustainable Aquatic Research Department of Biosciences College of Science Swansea University Swansea UK
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Muha TP, Rodriguez-Barreto D, O'Rorke R, Garcia de Leaniz C, Consuegra S. Using eDNA Metabarcoding to Monitor Changes in Fish Community Composition After Barrier Removal. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.629217] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Artificial instream barriers are a major cause of habitat fragmentation that reduce population connectivity and gene flow by limiting fish movements. To mitigate their impacts, obsolete barriers are increasingly been removed worldwide, but few barrier removal projects are monitored. We employed a powerful Before-After-Downstream-Upstream (BADU) approach using environmental DNA (eDNA) metabarcoding to examine the effects on fish community composition of removing a weir in the river Lugg (England) that had been suggested to have a detrimental effect on salmonid migration. We found no change in fish community diversity or relative abundance after the removal above or below the weir, but detected an important effect of sampling season, likely related to the species' life cycles. eDNA detected nine fish species that were also identified by electrofishing sampling and one additional species (Anguilla anguilla) that was missed by traditional surveys. Our results suggest that monitoring of barrier removal projects should be carried out to ensure that any ecological benefits are properly documented and that eDNA metabarcoding is a sensitive technique to monitor the effects of barrier removal.
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