Blood Lactate Concentrations and Mortality in Sockeye and Chinook Salmon (Oncorhynchus nerka and O. tshawytscha) After Exercise

Abstract

Blood lactate concentrations in 306 sockeye salmon (Oncorhynchus nerka), taken at sea in 1965 and 1966 by purse seine, gillnet, and longline, and in 98 starved or fed immature chinook salmon (O. tshawytscha) that had been exercised in a saltwater pond were generally below those reported in the literature as related to stress-induced mortality in salmon. No sockeye salmon held in shipboard tanks for observation died within 2 days after capture, although most of the fish died later. Few fish died among starved or fed immature chinook salmon in salt water within 10 days after capture by hook and line or after being chased to exhaustion; blood lactate concentrations in these fish were generally higher than in sockeye salmon after stress but were still usually below the reported critical level of 125 mg/100 ml.We concluded that neither the adult sockeye nor immature chinook salmon suffered immediate fatigue-related mortality, but the possibility that fatigue could induce delayed mortality was not excluded.