One size does not fit all: inter- and intraspecific variation in the swimming performance of contrasting freshwater fish.

Peter E Jones,Toby Champneys,Jon C Svendsen,Luca Börger,Carlos Garcia De Leaniz,Joshua A H Jones,Sofia Consuegra,Steven Cooke

doi:10.1093/conphys/coaa126

Peter E Jones, Toby Champneys + Show 6 more

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https://doi.org/10.1093/conphys/coaa126

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Abstract

Artificial barriers cause widespread impacts on freshwater fish. Swimming performance is often used as the key metric in assessing fishes' responses to river barriers. However, barrier mitigation is generally based on the swimming ability of salmonids and other strong swimmers because knowledge of swimming ability for most other freshwater fish is poor. Also, fish pass designs tend to adopt a 'one size fits all' approach because little is known about population or individual variability in swimming performance. Here, we assessed interspecific and intraspecific differences in the sustained swimming speed (Usus ) of five freshwater fish with contrasting body sizes, morphologies and swimming modes: topmouth gudgeon, European minnow, stone loach, bullhead and brown trout. Significant U sus variation was identified at three organizational levels: species, populations and individual. Interspecific differences in Usus were as large as 64cms-1, upstream populations of brown trout showed mean U sus 27cms-1 higher than downstream populations, and species exhibited high individual variation (e.g. cv = 62% in European minnow). Sustained swimming speed (U sus) increased significantly with body size in topmouth gudgeon, European minnow and brown trout, but not in the two benthic species, bullhead and stone loach. Aerobic scope had a significant positive effect on U sus in European minnow, stone loach and brown trout. Sustained swimming speed (U sus) decreased with relative pectoral fin length in European minnow and brown trout, whereas body fineness was the best predictor in stone loach and bullhead. Hence, swimming performance correlated with a diverse range of traits that are rarely considered when predicting fish passage. Our study highlights the dangers of using species' average swimming speeds and illustrates why a 'one size fits all' approach often fails to mitigate for barrier effects. We call for an evidence-based approach to barrier mitigation, one that recognizes natural variability at multiple hierarchical levels.

Highlights

Artificial barriers such as dams, weirs and culverts are ubiquitous in rivers worldwide (Lehner et al, 2011; Januchowski-Hartley et al, 2013; Grill et al, 2019; Belletti et al, 2020) and cause numerous impacts on freshwater fish populations, including habitat fragmentation (Morita and Yamamoto, 2002; Santucci Jr et al, 2005), disrupted migrations (Lucas and Baras, 2008) and reduced connectivity (Wofford et al, 2005), which can make populations more vulnerable to other anthropogenic pressures (Fagan, 2002)
European minnow, stone loach and bullhead were each collected from a single population, whereas brown trout was collected from two distinct catchments, each sampled from an upstream headwater and a downstream lowland site, to assess population-level variability in swimming performance
Brown trout was chosen for the population level study because they occur in a wide range of fluvial habitat types, ranging from small headwater streams to large slowflowing rivers

Summary

Introduction

Artificial barriers such as dams, weirs and culverts are ubiquitous in rivers worldwide (Lehner et al, 2011; Januchowski-Hartley et al, 2013; Grill et al, 2019; Belletti et al, 2020) and cause numerous impacts on freshwater fish populations, including habitat fragmentation (Morita and Yamamoto, 2002; Santucci Jr et al, 2005), disrupted migrations (Lucas and Baras, 2008) and reduced connectivity (Wofford et al, 2005), which can make populations more vulnerable to other anthropogenic pressures (Fagan, 2002). Swimming performance data are critical for the design of effective fish passes to provide passage over vertical barriers such as dams and weirs (Katopodis, 1992; Clay, 1995). There has been a tendency to focus on diadromous species when considering barrier effects, while river-resident taxa have largely been ignored (Lucas and Batley, 1996). This is perhaps due to the misconception that species that complete their lifecycles in rivers are sedentary and their longitudinal movements are negligible (Gerking, 1959). River-resident fish are impacted by barriers, and knowledge of these species’ swimming abilities is crucial for predicting barrier effects, as well as identifying effective mitigation options (Kemp and O’Hanley, 2010)

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