No abstract

No abstract

No abstract

The interaction between essential dietary components and changes in tissue nutrient reserves, egg quality and egg composition, were studied from 60 d before and during the spawning of Sparus aurata broodstock. Fish were given isonitrogenous (550 g/kg dry weight) and isolipidic (100 g/kg dry weight) diets, based on protein and lipid extracts of squid meal. Diets differed in the levels of n-6 (10-30 mg/g dry weight) and n-3 (0-10 mg/g dry weight) essential fatty acids. The effects of these diets on biochemical and fatty acid composition of body tissues, and the subsequent effects on egg composition and egg viability were measured. Dietary essential fatty acids were mostly incorporated into the liver, ovaries, digestive tract and associated adipose tissues. The lipid composition of these tissues reached an equilibrium with dietary lipid composition within 15 d of feeding on any given diet. Muscle and gill cartilage tissues did not show any significant changes in their biochemical and fatty acid composition, even after 60 d feeding. Egg viability decreased significantly within 10 d of feeding the broodstock with a diet deficient in n-3 highly unsaturated fatty acids (n-3 HUFA). The levels of n-3 HUFA in both polar and neutral fractions of egg lipid were directly correlated with their levels in the broodstock diet. When the total amount of egg n-3 HUFA dropped below 17 mg/g dry weight, egg viability and larvae hatching rate decreased by 53 YO and 47 YO respectively. These results suggest that the biochemical composition of organs involved in S. aurata reproduction are highly sensitive to the nutritional value of the diet, which affects egg and larval quality rapidly.Egg composition: Egg quality: n-3 fatty acids: Sparus uuruta Many fish species tend to decrease their food intake during sexual maturation, and the energy and nutrients needed for ovarian growth are taken from their body reserves. Tissue preference from which the reserves are mobilized is species specific; female trout (Salmo gairdneri R.) mainly mobilize carcass and visceral lipid reserves (Nassour & Leger, 1989), freshwater catfish (Clarias b a t r~~h u s ) use abdominal fat as the main energy source for sexual maturation (La1 & Singh, 1987), while farmed Atlantic salmon (Salmo salur) use both muscle lipid and protein during sexual maturation, with a resulting increase in body water content (Aksnes et al. 1986).Gilthead seabream (Sparus aurata) females continue to eat during sexual maturation and throughout the spawning season, and produce an egg biomass greater than their own body weight. In these circumstances material deposited in the ovaries must originate from the broodstock diet as well as from endogenous storage (carcass, liver and digestive tract), but the extent to which dietary or tissue reserves are utilized for ovarian growth, and how the diet quality affects the reproductive performance of this fish, is not known.

No abstract