When fish seek refuge from the main current, they can be described as ‘flow refuging’ . This behaviour usually occurs near the interface between a fluid and a solid, and can present an opportunity for ‘station holding’, which is the ability
to maintain position in a current relative to the earth frame of reference without actively swimming. This is the most commonly implicated mechanismofflow exploitation in the fisheries literature. The second mechanism involves capturing the energy of discrete,environmentally generated vortices, and this depends on an appropriate ratio of vortex diameter to fish length as well as low levels of background turbulence. These mechanisms are useful categories by which to think
about how fish use altered flows, but are to some extent arbitrary since both are ultimately taking advantage of
vortical flows.