Exhaustive Exercise in "Wild" Atlantic Salmon (Salmo saiar): Acid–Base Regulation and Blood Gas Transport

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Abstract
Wild Atlantic salmon (Salmo salar) collected during their spawning migration were transported to the laboratory to investigate effects of exhaustive exercise on acid–base regulation and blood gas transport. Exhaustive exercise resulted in a very large extracellular acidosis which lasted for about 4 h. Blood lactate levels were extremely high and remained significantly elevated for at least 8 h after exercise. The degree of erythrocyte pH regulation was minimal and there was a significant fall in both erythrocyte pH and haemoglobin:oxygen carriage during the recovery period. Together, the significant decrease in erythrocyte pH and a significant reduction in the arterial partial pressure of oxygen resulted in a significant fall in arterial oxygen content immediately after exercise. Thereafter, arterial oxygen content was maintained by a significant increase in hematocrit and an increase in the arterial partial pressure of oxygen. Despite the extremely large lactacidosis in these wild fish, there were no mortalities during the recovery period. However, significant mortality has been reported in studies on domestic salmonids, and this suggests that wild salmonids may be better adapted for exhaustive exercise. This result supports the rationale of a "catch and release" recreational fishery for Atlantic salmon.