Physiological effects of catch and release angling in Atlantic salmon (Salmo salar) at different stages of freshwater migration

The effects of exhaustive angling were investigated in one-sea-winter Atlantic salmon (Salmo salar) at two different stages of their freshwater migration. Physiological disturbances in kelts, returning to the ocean after a prolonged period of starvation, were compared with those of bright salmon, which had recently entered freshwater from the ocean. Condition factor was significantly higher in bright salmon than in kelts, and was associated with a greater time required to angle bright salmon to a state of exhaustion. White muscle concentrations of phosphocreatine and glycogen decreased in both kelts and bright salmon immediately after angling but recovered more quickly in kelts. White muscle lactate peaked after angling at 22.2 mmol . L(-1) tissue water in kelts and at 40.6 mmol . L(-1) tissue water in bright salmon. The intracellular acidosis that occurred in the white muscle following angling was also greater in bright salmon. Finally, mortality was not observed in any of the 24 angled kelts, but 3 of 25 bright salmon died within 12 h following angling. Together, these results demonstrate that the physiological disturbance from angling is smaller in kelts than in bright salmon.