Role of water flow regime in the swimming behaviour and escape performance of a schooling fish

Lauren E Nadler,Shaun S Killen,Paolo Domenici,Mark I Mccormick

doi:10.1242/bio.031997

Abstract

ABSTRACTAnimals are exposed to variable and rapidly changing environmental flow conditions, such as wind in terrestrial habitats and currents in aquatic systems. For fishes, previous work suggests that individuals exhibit flow-induced changes in aerobic swimming performance. Yet, no one has examined whether similar plasticity is found in fast-start escape responses, which are modulated by anaerobic swimming performance, sensory stimuli and neural control. In this study, we used fish from wild schools of the tropical damselfish Chromis viridis from shallow reefs surrounding Lizard Island in the Great Barrier Reef, Australia. The flow regime at each site was measured to ascertain differences in mean water flow speed and its temporal variability. Swimming and escape behaviour in fish schools were video-recorded in a laminar-flow swim tunnel. Though each school's swimming behaviour (i.e. alignment and cohesion) was not associated with local flow conditions, traits linked with fast-start performance (particularly turning rate and the distance travelled with the response) were significantly greater in individuals from high-flow habitats. This stronger performance may occur due to a number of mechanisms, such as an in situ training effect or greater selection pressure for faster performance phenotypes in areas with high flow speed.This article has an associated First Person interview with the first author of the paper.

Highlights

Environmental flow conditions can be variable and rapidly changing in many habitat types (Madin et al, 2006; McLaren et al, 2014)
Our study suggests that while school swimming behaviour is maintained across a range of localised water flow conditions, higher and more variable relative water flow speeds are associated with differences in individual fast-start performance
As fast-start responses are modulated by a range of sensory and neural processes as well as anaerobic swimming performance, flow is likely inducing change on a range of functional levels within individual fish through plasticity and/or selection

Summary

Introduction

Environmental flow conditions (e.g. wind in terrestrial habitats and currents in aquatic systems) can be variable and rapidly changing in many habitat types (Madin et al, 2006; McLaren et al, 2014). Variability in flow adds a level of complexity to activities such as foraging and navigation, for animals that fly or swim (Krupczynski and Schuster, 2008; Riley et al, 1999; Srygley, 2001; Thorup et al, 2003). Acute high-flow events could present problems for animal assemblages, as the behaviour and physiology of resident animals are likely suited to their habitat’s original conditions (Fulton and Bellwood, 2005; Johansen et al 2007; Munks et al, 2015; Nunes et al, 2013)

Methods

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Conclusion