Lack of Negative Effects of Fasting of Gilthead Seabream (Sparus Aurata) Breeders During the Spawning Period on Maternal and Egg Nutrient Composition, Fertilization Success and Early Embryo/larval Development

Abstract The effect of fasting on spawning performance, maternal and egg nutrient composition, and on embryo/larval development was monitored in gilthead seabream (Sparus aurata). Two broodstocks were fasted during two consequtive years, for a period of 43 and 54 days withing the spawning season, in a preliminary (year 1) and a main study (year 2), respectively. Mean daily fecundity showed a declining trend during fasting in the main study only, while fertilization success was high in both years and it was not affected by fasting, as was hatching and 5-day larval survival. There was a loss of 23.5% of maternal body mass due to fasting, and gonadosomatic and hepatosomatic indexes as well as crude protein in maternal muscle and gonads -but not in liver- were reduced after fasting. In muscle, after fasting Σω-6 PUFA and C18:3ω-3 were reduced while C20:4ω-6, 20:5ω-3/20:4ω-6 and C22:6ω-3/20:4ω-6 increased; in liver, significant reductions were observed in C16:0, C18:3 ω-3, 20:5ω-3/C22:6ω-3 and increases in C18:0, C20:5ω-3, Σω-6 PUFA and 20:5ω-3/20:4ω-6; in gonads, C15:0, ΣMUFA, 20:5ω-3/C22:6ω-3, 20:5ω-3/20:4ω-6 were increased while C18:1ω-9, C20:5ω-3 reduced. Contrary to maternal tissues, the energy density and proximate composition of the eggs did not change due to fasting. The study suggests that fasting of gilthead seabream breeders for many weeks during the spawning period does not affect spawning performance, egg proximate composition or embryo and early larval development, since maternal nutrient reserves are mobilized to maintain optimal egg nutrient composition.