Oxygen consumption in relation to current velocity and morphology in the highly invasive crayfish Procambarus clarkii

The red swamp crayfish ( Procambarus clarkii ) is the most widely spread freshwater crayfish worldwide. Competing physiological traits can influence invasion success in any given environment by limiting the available scope for aerobically demanding activities. While high flows have been associated with reduced crayfish movement upstream, the effects of flow alteration on their metabolic demands have been largely overlooked. In this study, we estimated routine metabolic rate (RMR) at rest and oxygen consumption rates of crayfish under different current velocities in a flume respirometer, while maximum metabolic rate (MMR) was determined using the exhaustive chase protocol. We also measured some morphometric variables in males and females of crayfish. Oxygen uptake substantially increased with crayfish size and current velocity due to increased energy expenditure to overcome drag and hold a stationary position. Sexual dimorphism in morphological traits did not lead to sexual differences in oxygen uptake. Moreover, we found that individuals operated close to their maximum aerobic capacity at elevated current velocities (≥ 25 cm s −1 ). This suggested that the high flow-driven energetic demand may compromise the energy available for reproduction, growth and dispersal, thereby affecting overall fitness. These metabolic constraints could partly explain the failed invasions of invasive crayfish in fast-flowing waters.