Behavioural and metabolic aspects of recovery from intense exercise in juvenile rainbow trout, Oncorhynchus mykiss
I investigated the behavioural and metabolic recovery of juvenile rainbow trout after single and multiple bouts of intense exercise (sprints). The behavioural end point of a sprint is unambiguous as fish stop swimming at a specified velocity. Partially powered by anaerobic metabolism, one sprint reduces the endogenous supply of the energy metabolites, ATP, CP and glycogen in the white muscle and produces lactate. Despite the cessation of swimming and the reduction of anaerobic energy after a single sprint, my study showed that with recovery intervals lasting only 3 minutes in duration, fish were able to resume swimming a minimum of eight times. Fish performed intermittent exercise by progressively decreasing the contribution of anaerobic energy until expenditure had completely stopped by the eighth sprint, despite the availability of anaerobic metabolites. This finding inferred that successive sprints were sustained entirely by aerobic metabolism and that fish were swimming in a steady state.