ABSTRACT
This chapter focuses on the hydrodynamic environment experienced by fishes—and other biota—specifically on turbulence, a ubiquitous feature of aquatic habitats that has largely been neglected. The natural habitats of fishes are characterized by water movements driven by gravity, wind, and other animals, including human activities such as shipping. Unsteady water movements have many effects on fishes but the mechanical basis for understanding the nature of responses is poorly known. Eddy-dominated flow is more common in fish habitat than nonbreaking wave-induced orbits. The orbits of wave-induced water movements and eddies in currents are perturbations with the capability of destabilizing postures and trajectories of fishes embedded in the incident water movements. Systematic studies that compare the structure of incident water movements with fish behavior are still lacking but are essential to determine the size limits of eddies that create problems for fishes.
