A model of total swimming costs in turbulent flow for juvenile Atlantic salmon ( Salmo salar )

Juvenile Atlantic salmon (Salmo salar) live in rivers characterized by highly turbulent flows. In these environments, flow turbulence is associated with a wide range of instantaneous flow velocities, which may affect the energetic costs of habitat utilization of juvenile Atlantic salmon. The purpose of our work was to develop a swimming costs model for juvenile Atlantic salmon that especially accounts for the effects of velocity fluctuations in turbulent environments. We estimated the total swimming costs of fish in a respirometer in which we produced five turbulent flow conditions, each characterized by a mean and a standard deviation of flow. Respirometry experiments were conducted at water temperatures of 10, 15, and 20 °C with fish ranging in size between 4.3 and 17.6 g at three mean flow velocities (18, 23, and 40 cm·s –1 ) and three standard deviations of flow velocity (5, 8, and 10 cm·s –1 ). Our results confirmed that total swimming costs increased with an increase of water temperature, body mass, mean flow velocity, and standard deviation of flow velocity (R 2 = 0.93). Water temperature, body mass, mean flow velocity, and standard deviation of flow velocity contributed respectively 2%, 31%, 46%, and 14% to the explained variation in total swimming costs.