Physiology and Survival of Wild Atlantic Salmon following Angling in Warm Summer Waters

Abstract

Atlantic salmon Salmo salar, returning to freshwater to spawn, were angled and then terminally sampled to test the hypothesis that angling during warmer summer months (water temperatures of 20 ± 2°C) increases the magnitude of physiological disturbances in the white muscle. Angling immediately reduced white muscle ATP and phosphocreatine stores, but these high-energy phosphates were replenished within 2–4 h. Intramuscular glycogen stores were nearly depleted after angling, but unlike the response by salmon angled in the fall at 6°C, there was no glycogen resynthesis during the 4-h recovery period. Marked increases in white muscle lactate and the postexercise metabolic proton load (▵H+m) accompanied glycogen depletion. The time course of lactate elimination and ▵H+m correction, however, was much slower than previously observed in fall-angled salmon. Finally, considerable delayed postangling mortality (40%) was observed in a subgroup of Atlantic salmon that were angled at 22°C. We conclude that angling in warm summer water impairs restorative processes and increases the susceptibility of Atlantic salmon to delayed postangling mortality. We suggest that anglers can mitigate the magnitude of angling-induced physiological disturbances in Atlantic salmon during midsummer by minimizing playing time and postangling air exposure.