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Elings J, Bruneel S, Pauwels IS, Schneider M, Kopecki I, Coeck J, Mawer R, Goethals PLM. Finding navigation cues near fishways. Biol Rev Camb Philos Soc 2024; 99:313-327. [PMID: 37813384 DOI: 10.1111/brv.13023] [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: 07/15/2022] [Revised: 09/27/2023] [Accepted: 09/28/2023] [Indexed: 10/11/2023]
Abstract
Many fish species depend on migration for various parts of their life cycle. Well-known examples include diadromous fish such as salmon and eels that need both fresh water and salt water to complete their life cycle. Migration also occurs within species that depend only on fresh water. In recent decades, anthropogenic pressures on freshwater systems have increased greatly, and have resulted, among other effects, in drastic habitat fragmentation. Fishways have been developed to mitigate the resulting habitat fragmentation, but these are not always effective. To improve fishway efficiency, the variety of navigation cues used by fish must be better understood: fish use a multitude of sensory inputs ranging from flow variables to olfactory cues. The reaction of a fish is highly dependent on the intensity of the cue, the fish species involved, and individual traits. Recently developed monitoring technologies allow us to gain insights into different combinations of environmental and physiological conditions. By combining fish behavioural models with environmental models, interactions among these components can be investigated. Several methods can be used to analyse fish migration, with state-space models, hidden Markov models, and individual-based models potentially being the most relevant since they can use individual data and can tie them to explicit spatial locations within the considered system. The aim of this review is to analyse the navigational cues used by fish and the models that can be applied to gather knowledge on these processes. Such knowledge could greatly improve the design and operation of fishways for a wider range of fish species and conditions.
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Affiliation(s)
- Jelger Elings
- Aquatic Ecology Research Unit, Department of Animal Sciences and Aquatic Ecology, Ghent University, Coupure Links 653, Ghent, B-9000, Belgium
| | - Stijn Bruneel
- Aquatic Ecology Research Unit, Department of Animal Sciences and Aquatic Ecology, Ghent University, Coupure Links 653, Ghent, B-9000, Belgium
| | - Ine S Pauwels
- INBO, Team Aquatic Management, Research Institute for Nature and Forest, Havenlaan 88, Brussel, Belgium
| | - Matthias Schneider
- SJE Ecohydraulic Engineering GmbH, Dilleniusstrasse 13, Backnang, 71522, Germany
| | - Ianina Kopecki
- SJE Ecohydraulic Engineering GmbH, Dilleniusstrasse 13, Backnang, 71522, Germany
| | - Johan Coeck
- INBO, Team Aquatic Management, Research Institute for Nature and Forest, Havenlaan 88, Brussel, Belgium
| | - Rachel Mawer
- Aquatic Ecology Research Unit, Department of Animal Sciences and Aquatic Ecology, Ghent University, Coupure Links 653, Ghent, B-9000, Belgium
| | - Peter L M Goethals
- Aquatic Ecology Research Unit, Department of Animal Sciences and Aquatic Ecology, Ghent University, Coupure Links 653, Ghent, B-9000, Belgium
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Carolli M, Garcia de Leaniz C, Jones J, Belletti B, Huđek H, Pusch M, Pandakov P, Börger L, van de Bund W. Impacts of existing and planned hydropower dams on river fragmentation in the Balkan Region. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 871:161940. [PMID: 36736393 DOI: 10.1016/j.scitotenv.2023.161940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 12/18/2022] [Accepted: 01/27/2023] [Indexed: 06/18/2023]
Abstract
The Balkan region has some of the best conserved rivers in Europe, but is also the location of ~3000 planned hydropower dams that are expected to help decarbonise energy production. A conflict between policies that promote renewable hydropower and those that prioritise river conservation has ensued, which can only be resolved with the help of reliable information. Using ground-truthed barrier data, we analysed the extent of current longitudinal river fragmentation in the Balkan region and simulated nine dam construction scenarios that varied depending on the number, location and size of the planned dams. Balkan rivers are currently fragmented by 83,017 barriers and have an average barrier density of 0.33 barriers/km after correcting for barrier underreporting; this is 2.2 times lower than the mean barrier density found across Europe and serves to highlight the relatively unfragmented nature of these rivers. However, our analysis shows that all simulated dam construction scenarios would result in a significant loss of connectivity compared to existing conditions. The largest loss of connectivity (-47 %), measured as reduction in barrier-free length, would occur if all planned dams were built, 20 % of which would impact on protected areas. The smallest loss of connectivity (-8 %) would result if only large dams (>10 MW) were built. In contrast, building only small dams (<10 MW) would cause a 45 % loss of connectivity while only contributing 32 % to future hydropower capacity. Hence, the construction of many small hydropower plants will cause a disproportionately large increase in fragmentation that will not be accompanied by a corresponding increase in hydropower. At present, hydropower development in the Balkan rivers does not require Strategic Environmental Assessment, and does not consider cumulative impacts. We encourage planners and policy makers to explicitly consider trade-offs between gains in hydropower and losses in river connectivity at the river basin scale.
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Affiliation(s)
| | | | | | | | - Helena Huđek
- Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Germany
| | - Martin Pusch
- Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Germany
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3
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Bopp JJ, Brenden TO, Faust MD, Vandergoot CS, Kraus RT, Roberts JJ, Nathan LR. Drivers and timing of grass carp movement within the Sandusky River, Ohio: implications to potential spawning barrier response strategy. Biol Invasions 2023. [DOI: 10.1007/s10530-023-03049-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
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Sun J, Du W, Lucas MC, Ding C, Chen J, Tao J, He D. River fragmentation and barrier impacts on fishes have been greatly underestimated in the upper Mekong River. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 327:116817. [PMID: 36459786 DOI: 10.1016/j.jenvman.2022.116817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 11/09/2022] [Accepted: 11/14/2022] [Indexed: 06/17/2023]
Abstract
River barriers reduce river connectivity and lead to fragmentation of fish habitats, which can result in decline or even extinction of aquatic biota, including fish populations. In the Mekong basin, previous studies have mainly focused on the impacts of large dams but ignored the impacts of small-scale barriers, or drew conclusions from incomplete barrier databases, potentially leading to research biases. To test the completeness of existing databases and to evaluate the catchment-scale fragmentation level, a detailed investigation of river barriers for the whole Upper Mekong (Lancang catchment) was performed, by conducting visual interpretation of high-resolution remotely sensed images. Then, a complete catchment-scale barrier database was created for the first time. By comparing our barrier database with existing databases, this study indicates that 93.7% of river barriers were absent from the existing database, including 75% of dams and 99.5% of small barriers. Barrier density and dendritic connectivity index (DCID and DCIP) were used to measure channel fragmentation within the catchment. Overall, 50.5% of sub-catchments contained river barriers. The Middle region is the most fragmented area within the Lancang catchment, with a median [quartiles] barrier density of 5.34 [0.70-9.67] per 100 km, DCIP value of 49.50 [21.50-90.00] and DCID value of 38.50 [9.00-92.25]. Furthermore, since 2010, distribution ranges of two representative fish species Schizothorax lissolabiatus (a rheophilic cyprinid) and Bagarius yarrelli (a large catfish) have reduced by 19.2% and 32.8% respectively, probably due in part to the construction of river barriers. Our findings indicate that small-scale barriers, in particular weirs and also small dams are the main reason for habitat fragmentation in the Lancang and must be considered alongside large dams in water management and biodiversity conservation within the Mekong.
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Affiliation(s)
- Jingrui Sun
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China
| | - Weilong Du
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China
| | - Martyn C Lucas
- Department of Biosciences, University of Durham, Durham DH1 3LE, UK
| | - Chengzhi Ding
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China.
| | - Jinnan Chen
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China
| | - Juan Tao
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China
| | - Daming He
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China.
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5
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Kiffney PM, Lisi PJ, Liermann M, Naman SM, Anderson JH, Bond MH, Pess GR, Koehler ME, Buhle ER, Buehrens TW, Klett RS, Cram JM, Quinn TP. Colonization of a temperate river by mobile fish following habitat reconnection. Ecosphere 2023. [DOI: 10.1002/ecs2.4336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023] Open
Affiliation(s)
- P. M. Kiffney
- Fish Ecology, Northwest Fisheries Science Center National Marine Fisheries Service, NOAA Seattle Washington USA
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington USA
| | - P. J. Lisi
- Washington Department of Fish and Wildlife Olympia Washington USA
| | - M. Liermann
- Fish Ecology, Northwest Fisheries Science Center National Marine Fisheries Service, NOAA Seattle Washington USA
| | - S. M. Naman
- Department of Zoology University of British Columbia Vancouver British Columbia Canada
- Fisheries and Oceans Canada Freshwaer Ecosystems Section Cultus Lake British Columbia Canada
| | - J. H. Anderson
- Washington Department of Fish and Wildlife Olympia Washington USA
| | - M. H. Bond
- Fish Ecology, Northwest Fisheries Science Center National Marine Fisheries Service, NOAA Seattle Washington USA
| | - G. R. Pess
- Fish Ecology, Northwest Fisheries Science Center National Marine Fisheries Service, NOAA Seattle Washington USA
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington USA
| | | | - E. R. Buhle
- Affiliate, Northwest Fisheries Science Center National Marine Fisheries Service, NOAA Seattle Washington USA
- Mount Hood Environmental Sandy Oregon USA
| | - T. W. Buehrens
- Washington Department of Fish and Wildlife Ridgefield Washington USA
| | - R. S. Klett
- Colville Indian Tribes Nespelem Washington USA
| | - J. M. Cram
- Washington Department of Fish and Wildlife Wenatchee Washington USA
| | - T. P. Quinn
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington USA
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Kume M, Yoshikawa Y, Tanaka T, Watanabe S, Mitamura H, Yamashita Y. Water temperature and precipitation stimulate small-sized Japanese eels to climb a low-height vertical weir. PLoS One 2022; 17:e0279617. [PMID: 36574439 PMCID: PMC9794052 DOI: 10.1371/journal.pone.0279617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 12/12/2022] [Indexed: 12/28/2022] Open
Abstract
Although river-crossing structures can have a detrimental effect on the movement and distribution of anguillid eels (genus Anguilla), they have inhabited locations upstream of river-crossing structures in many rivers. However, the growth stage in which the eels start to climb river-crossing structures remains unclear. In this study, we directly observed, using infrared video camera systems, that the Japanese eel (Anguilla japonica) climbs a low-height vertical weir as a migratory barrier, confirming the ability of eels to climb over a low-height weir within a river. All eels climbed the weir at night, between sunset and sunrise. We observed that the total length of Japanese eels that climbed the weir ranged from 60 to 140 mm, suggesting that eels inhabiting the upstream area of a weir climbed it when they were small and then lived and grew upstream. Moreover, the general additive model showed considerable effects of water temperature and precipitation on eel climbing, suggesting that water temperature and precipitation are important for its activation. The results of this study also show the effectiveness of infrared video cameras in monitoring eel climbing, which could be applied to monitor fish migratory behavior through fish passages. The findings of this study are useful for the comprehensive management and conservation of wild eel stocks.
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Affiliation(s)
- Manabu Kume
- Field Science Education and Research Center, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto, Japan
| | - Yudai Yoshikawa
- Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto, Japan
| | | | - Shun Watanabe
- Faculty of Agriculture, Kindai University, Nara, Japan
| | - Hiromichi Mitamura
- Field Science Education and Research Center, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto, Japan
- Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto, Japan
| | - Yoh Yamashita
- Field Science Education and Research Center, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto, Japan
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Garcia de Leaniz C, O'Hanley JR. Operational methods for prioritizing the removal of river barriers: Synthesis and guidance. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 848:157471. [PMID: 35868378 DOI: 10.1016/j.scitotenv.2022.157471] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/30/2022] [Accepted: 07/14/2022] [Indexed: 06/15/2023]
Abstract
Barrier removal can be an efficient method to restore river continuity but resources available for defragmenting rivers are limited and a prioritization strategy is needed. We review methods for prioritizing barriers for removal and report on a survey asking practitioners which barrier prioritization methods they use. Opportunities for barrier removal depend to a large extent on barrier typology, as this dictates where barriers are normally located, their size, age, condition, and likely impacts. Crucially, river fragmentation depends chiefly on the number and location of barriers, not on barrier size, while the costs of barrier removal typically increase with barrier height. Acting on many small barriers will often be more cost-efficient than acting on fewer larger structures. Barriers are not randomly distributed and a small proportion of barriers have a disproportionately high impact on fragmentation, therefore targeting these 'fragmentizers' can result in substantial gains in connectivity. Barrier prioritization methods can be grouped into six main types depending on whether they are reactive or proactive, whether they are applied at local or larger spatial scales, and whether they employ an informal or a formal approach. While mathematical optimization sets the gold standard for barrier prioritization, a hybrid approach that explicitly considers uncertainties and opportunities is likely to be the most effective. The effectiveness of barrier removal can be compromised by inaccurate stream networks, erroneous barrier coordinates, and underestimation of barrier numbers. Such uncertainties can be overcome by ground truthing via river walkovers and predictive modelling, but the cost of collecting additional information must be weighed against the cost of inaction. To increase the success of barrier removal projects, we recommend that barriers considered for removal fulfill four conditions: (1) their removal will bring about a meaningful gain in connectivity; (2) they are cost-effective to remove; (3) they will not cause significant or lasting environmental damage, and (4) they are obsolete structures. Mapping barrier removal projects according to the three axes of opportunities, costs, and gains can help locate any 'low hanging fruit.'
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Affiliation(s)
- Carlos Garcia de Leaniz
- Department of Biosciences, Centre for Sustainable Aquatic Research (CSAR), Swansea University, Swansea, UK.
| | - Jesse R O'Hanley
- Kent Business School, University of Kent, Canterbury, UK; Durrell Institute of Conservation and Ecology, University of Kent, Canterbury, UK
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8
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Conservation of endangered galaxiid fishes in the Falkland Islands requires urgent action on invasive brown trout. Biol Invasions 2022. [DOI: 10.1007/s10530-022-02959-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
AbstractNon-native salmonids are protected in the Southern hemisphere where they sustain aquaculture and lucrative sport fisheries, but also impact many native fishes, which poses a conservation conundrum. Legal protection and human-assisted secondary releases may have helped salmonids to spread, but this has seldom been tested. We reconstructed the introduction of brown trout (Salmo trutta) to the Falkland Islands using historical records and modelled its dispersal and probability of invasion using a generalized linear model and Leave One out Cross Validation. Our results indicate that establishment success was ~ 88%, and that dispersal was facilitated over land by proximity to invaded sites and density of stream-road crossings, suggesting it was human assisted. Brown trout have already invaded 54% of Falkland rivers, which are 2.9–4.5 times less likely to contain native galaxiids than uninvaded streams. Without strong containment we predict brown trout will invade nearly all suitable freshwater habitats in the Falklands within the next ~ 70 years, which might put native freshwater fishes at a high risk of extinction.
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9
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A national fish passage barrier inventory to support fish passage policy implementation and estimate river connectivity in New Zealand. ECOL INFORM 2022. [DOI: 10.1016/j.ecoinf.2022.101831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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10
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Personality-dependent passage behaviour of an aquatic invasive species at a barrier to dispersal. Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Mensinger MA, Brehm AM, Mortelliti A, Blomberg EJ, Zydlewski JD. American eel personality and body length influence passage success in an experimental fishway. J Appl Ecol 2021. [DOI: 10.1111/1365-2664.14009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Matthew A. Mensinger
- Department of Wildlife, Fisheries, and Conservation Biology University of Maine Orono ME USA
| | - Allison M. Brehm
- Department of Wildlife, Fisheries, and Conservation Biology University of Maine Orono ME USA
| | - Alessio Mortelliti
- Department of Wildlife, Fisheries, and Conservation Biology University of Maine Orono ME USA
| | - Erik J. Blomberg
- Department of Wildlife, Fisheries, and Conservation Biology University of Maine Orono ME USA
| | - Joseph D. Zydlewski
- Department of Wildlife, Fisheries, and Conservation Biology University of Maine Orono ME USA
- Maine Cooperative Fish and Wildlife Research Unit U.S. Geological Survey University of Maine Orono ME USA
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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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Lothian AJ, Lucas MC. The role of individual behavioral traits on fishway passage attempt behavior. Ecol Evol 2021; 11:11974-11990. [PMID: 34522354 PMCID: PMC8427575 DOI: 10.1002/ece3.7964] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 06/18/2021] [Accepted: 07/13/2021] [Indexed: 11/08/2022] Open
Abstract
Variations in behavioral traits are widely recognized to drive animal behaviors exhibited within a population. However, information on how behavior traits influence behavior in anthropogenically modified habitats is lacking. Many habitats have become highly fragmented as a result of human processes. To mitigate this and improve habitat connectivity, wildlife passes are increasingly employed, with the aim of enabling animals to move freely between habitats. However, wildlife passes (e.g., fishways) are not always effective in achieving passage and it remains uncertain what factors play a role in an individual's likelihood of passing successfully. This study measured three behavioral traits (boldness, exploration, and activity) in juvenile brown trout (Salmo trutta; n = 78) under field conditions within a river and tested whether these behavior traits influenced both the passage success and the behaviors exhibited during upstream fishway passage attempts. Although behavioral traits were found and collapsed into two behavioral trait dimensions, behavioral traits had low repeatability and so did not contribute to a personality spectrum. Boldness was found to negatively influence the number of passage attempts carried out by an individual and to positively influence passage success, with bolder individuals carrying out fewer attempts and having an increased probability of passage success. No behavioral traits were found to be related to other passage metrics (passage success, Time until First Attempt, and Passage Duration) during the first passage. But all three behavioral traits were significantly negatively related to the changes in passage behaviors at consecutive, successful passage attempts, with bolder, more exploratory and more active individuals passing through a fishway quicker on the second passage than on the first. This study suggests that bolder and more active individuals may perform better during fishway passage attempts, particularly within rivers where multiple barriers to movement exist.
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