Effect of protein supplement on blood plasma amino acids of coho salmon in culture in seawater during summer

Abstract Coho salmon, Oncorhynchus kisutch , aged 1 year (1+), were held in seawater in floating cages on the Brittany coast during summer 1980. A supplemental feed containing soluble protein and ascorbic acid was given to prevent the high mortality which occurs at this time of year. Blood plasma amino acids of control and supplemented animals were evaluated by ion exchange chromatography. Results indicated that ornithine, alanine, valine, isoleucine, leucine and tyrosine levels increase during summer, whereas histidine decreases. Supplementation for 50 days did not affect these changes, but after 90 days the amino acid pattern of supplemented animals approached the initial control. Supplemental feeding did not diminish mortality (85%) which is thus probably not related to exhaustive proteolysis but rather to environmental factors or undetected infection.