Alterations in the Blood Level of Lactic Acid in Certain Salmonoid Fishes Following Muscular Activity: I. Kamloops Trout, Salmo gairdneri

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Abstract
During the summers of 1953, 1954 and 1955, experiments were carried out on the effects of muscular exercise on hatchery-raised yearling and two-year-old Kamloops trout, Salmo gairdneri, at the Summerland Trout Hatchery, Summerland, B.C. Following 15 minutes of vigorous exercise at 11.5 °C. the blood level of lactic acid in yearlings increased from the unexercised level of 16 mg.% to 100 mg.% and then continued to increase still further during the first 2 hours of recovery to 170 mg.%, to subside in 4 to 6 hours toward the pre-exercise level. Similar changes occurred in two-year-olds, but the levels were lower in all cases, and the time course was slower. Studies were also made on hemoglobin levels, on blood glucose changes in two-year-olds, and on the relation of oxygen levels and temperature to the blood levels of lactic acid in yearlings. Cardiac rates were also measured. Observations were made on the blood level of lactic acid in moderate exercise in yearlings. The results indicate that most of the features of fatigue in the trout are in keeping with the pattern of changes in mammals. However, there were important differences in the time course of rise and fall of lactic acid to and from the blood. It is suggested that these differences may be due to the effects of lowered temperature in reducing the rate of diffusion of lactic acid between extracellular fluids and the sites of production and removal of the metabolites of muscular activity. Some implications of the results to the behaviour of fishes and death due to over-exertion are discussed.