Temperature influences sociality and activity of freshwater fish

Temperature is a critical environmental factor in the ecology of fish, significantly influencing their physiology and behavior. Previous studies on the effect of temperature have focused on the metabolic and growth rates of individual fish and on the social behavior of fish shoals in placid water. In this paper, we investigate the effect of changing temperature on shoals of giant danios as they swim in a water tunnel at 22, 25, and 28 A degrees C. Fish activity is quantified in terms of rheotaxis and tail-beat frequency measured automatically by tracking fish shape. Fish social behavior is quantified in terms of average nearest neighbor distance (ANND) and polarization. Results show that both social behavior and individual activity are significantly affected by change in temperature. In particular, fish maximize their activity and ANND at 28 A degrees C, while their polarization is maximized at 22 A degrees C. These findings suggest that temperature influences both the social behavior and the energy expenditure of fish, whereby lower temperatures lead to more cohesive shoals with reduced fish activity.