PROTEIN-METABOLISM DURING SEXUAL-MATURATION IN FEMALE ATLANTIC SALMON(SALMO-SALAR L)

Body composition and fractional rates of protein synthesis (percentage of the protein mass synthesized per day) were determined in female At lantic salmon returning to the River Tay, Scotland in July and in Octo ber after a 95 day period without food, during which time the animals became sexually mature. During the 95 day period of starvation/sexual maturation the ventricle and red muscle remained as a constant proport ion of fresh weight whereas the liver, gill and ovary increased and th e stomach and white muscle decreased. Fractional rates of protein synt hesis increased markedly in the liver, stomach and ovary during the pe riod of starvation/sexual maturation. In the gill, ventricle and white muscle fractional protein synthesis rates increased slightly or remai ned constant. From the estimated rates of protein loss or gain in the various tissues it is concluded that there is considerable protein tur nover and repartitioning of amino acids during the period of starvatio n and sexual maturation. The absolute rate of protein synthesis rates in the ovary indicates that this tissue made the largest contribution to the energy and amino acid demands of the fish, whilst most of the a mino acids required for maturation of the ovary were derived from whit e muscle, principally as the result of increased muscle protein degrad ation.