The Challenge of Understanding and Quantifying Fish Responses to Turbulence-Dominated Physical Environments

The natural habitats of fishes are characterized by water movements driven by a multitude of physical processes of either natural or human origin. The resultant unsteadiness is exacerbated when flow interacts with surfaces, such as the bottom and banks, and protruding objects, such as corals, boulders, and woody debris. There is growing interest in the impacts on performance and behavior of fishes swimming in “turbulent flows”. The ability of fishes to stabilize body posture and their swimming trajectories is thought to be important in determining species distributions and densities, and hence resultant assemblages in various habitats. Understanding impacts of turbulence and vorticity on fishes is important as human practices modify water movements, and as turbulence-generating structures ranging from hardening shorelines to control erosion, through designing fish deterrents, to the design of fish passageways become common. Collaboration between engineers and biologists is essential in order to generate adequate and sustainable solutions. Previous work on fish responses to turbulent perturbations is discussed and new theoretical concepts/framework are proposed to quantify fish-eddy interactions.