However, care needs to be exercised when extrapolating data to group situations. Reduced tail-beat frequency is thought to correspond to reduced energy expenditure based on the assumption that individuals benefit from flow refuging, wall effects, vortex capture or some combination of these mechanisms. Despite the occurrence of decreased tailbeat
frequency for schooling fishes, additional data are needed before we can distinguish between these hydrodynamic mechanisms. Observations of individual positions in a school have provided useful information, but still almost no hydrodynamic or physiological data exist to evaluate the hypothesis that fish can increase swimming performance by taking advantage of the wake of other.