strong as they can be observed to negotiate. Sincethen, many studies have shown that vortical flows provide an energy-rich environment which can be exploited to enhance swimming performance. There are at least two mechanisms by which fish can exploit unsteady flows generated by abiotic or biotic sources to increase swimming performance. First, fish can take advantage of regions of reduced flow velocity behind bluff bodies. In this case, the average velocity in the turbulent wake is
reduced relative to both its steady-state condition prior to interaction with the bluff body and to the earth frame of reference.