Abstract
Global climate change continues to impact fish habitat quality and biodiversity, especially in regard to the dynamics of invasive non-native species. Using individual aquaria and an open channel flume, this study evaluated the effects of water temperature, flow velocity and turbulence interactions on swimming performance of two lentic, invasive non-native fish in the UK, pumpkinseed (Lepomis gibbosus) and topmouth gudgeon (Pseudorasbora parva). Burst and sustained swimming tests were conducted at 15, 20 and 25°C. Acoustic Doppler velocimetry was used to measure the flume hydrodynamic flow characteristics. Both L. gibbosus and P. parva occupied the near-bed regions of the flume, conserving energy and seeking refuge in the low mean velocities flow areas despite the relatively elevated turbulent fluctuations, a behaviour which depended on temperature. Burst swimming performance and sustained swimming increased by up to 53% as temperature increased from 15 to 20°C and 71% between 15 and 25°C. Furthermore, fish test area occupancy was dependent on thermal conditions, as well as on time-averaged velocities and turbulent fluctuations. This study suggests that invasive species can benefit from the raised temperatures predicted under climate change forecasts by improving swimming performance in flowing water potentially facilitating their further dispersal and subsequent establishment in lotic environments.
Highlights
Human alterations to freshwater ecosystems through hydro-engineering and water management activities, combined with global climate change, continue to alter the aquatic environment
Temperature had a significant effect on the burst swimming speed of L. gibbosus (GLM, p < 0.001) but did not significantly affect that of P. parva (GLM, p > 0.05)
Lepomis gibbosus burst speeds were faster by 43% at 20°C and 53% at 25°C than those tested at 15°C (GLM, p < 0.05)
Summary
Human alterations to freshwater ecosystems through hydro-engineering and water management activities, combined with global climate change, continue to alter the aquatic environment. Since temperature directly affects fish metabolism [19], some species benefit from temperature increases, which improves their swimming velocities, while others respond negatively [12]. This key effect of thermal regimes on swimming performance is likely to intensify due to global warming, which will change storm frequency, timing and duration, and the resulting river runoff regimes, but most importantly water quality and temperature, with direct impacts on aquatic ecosystems [4,20,21,22]
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