Hydrodynamics and Energetics of Schooling Swimming and Migration of Schooling Fish

Ideas about the hydrodynamic and energetic benefits of swimming in a school have been considered. The reduction in energy cost for locomotion in a school is achieved due to the interference of microvortices generated by fish moving or staying in the current (hydrodynamic hypothesis of schooling swimming). The effect is most pronounced if the fish are of the same size, have similar locomotor capabilities, and show consistency when changing the mode or direction of swimming. It is also believed that the hydrodynamic effect of a school is realized only when partners in intra-school subgroups interact. Increased endurance of fish when in a school compared to single individuals has been experimentally confirmed. Energy costs for swimming while in a school can be lower by about 10–20%. Most of the fish that make long migrations are schooling fish, or form schools for the period of migration. Combining small schools into larger schools and school aggregations (mega-schools) facilitates finding optimal paths and improves the accuracy of migrations. Migration in schools reduces the vulnerability of fish to predators.