Swimming through turbulent water is easier for schooling fish compared to solitary swimmers. The turbulent sheltering hypothesis, which suggests that traveling in schools allows fish to shield each other from disruptive water currents, thus making it easier to swim through rough waters. The researchers tested their hypothesis using giant danios (Devario aeqipinnatus), and observed these fish swimming alone or in groups of eight in both turbulent and steadily flowing water. The trials revealed that schooling fish expended up to 79% less energy while swimming in turbulent water compared to solitary fish. Schooling fish also clustered more closely together in turbulent water compared to steady water, while solitary fish had to beat their tails much more vigorously to maintain the same speed in more turbulent currents. These results lend support to the “turbulence sheltering hypothesis,” indicating that locomotion efficiency might be a driving factor behind the evolution of schooling behaviour. Being in a school substantially reduces the energetic cost for fish swimming in a turbulent environment, compared to swimming alone. Schooling behaviour protects individual fish from the increased energetic cost associated with swimming in turbulence.
