BIOCHEMICAL STUDIES ON SOCKEYE SALMON DURING SPAWNING MIGRATION: I. PHYSICAL MEASUREMENTS, PLASMA CHOLESTEROL, AND ELECTROLYTE LEVELS

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Abstract
Physical measurements have been made on all major organs and tissues of a pure race of migrating adult Oncorhynchus nerka. The data show that the population was sufficiently uniform in size that average weights and measurements performed on fish taken at three locations on the migration route quite accurately represented a standard fish of both sexes. The results will enable chemical analyses to be interpreted as changes in absolute amounts of a given tissue component rather than only on a percentage basis. The merits of this approach to an evaluation of changes in migrating salmon is demonstrated by the magnitude of the weight changes in many tissues during the 715-mile migration. A standard male lost only 11% of its body flesh whereas a standard female lost 30%. The alimentary tract decreased to one sixth of the initial weight. The milt increased by 51% while the roe increased by 272%. Thus, it is apparent that percentage composition data cannot show quantitative changes in a fish as it moves up the river. The results are discussed in relation to the findings of others on Salmonidae. Plasma cholesterol, magnesium, calcium, sulphate, and urea levels were measured on pooled blood samples from the 216 fish.