Effect of broodstock nutrition on reproductive performance of fish

In many cultured fish species, particularly in those new for aquaculture, u npredictable and variable reproductive performance is an important limiting factor for the successful mass production of juveniles. An improvement in broodstock nutrition and feeding has been shown to greatly improve not only egg and sperm quality but also seed production. Gonadal development and fe cundity are affected by certain essential dietary nutrients, especially in continuous spawners with short virellogenic periods. Thus, during the last two decades, more attention has been paid to the level of different nutrien ts in broodstock diets. However, studies on broodstock nutrition are limite d and relatively expensive to conduct. Lipid and fatty acid composition of broodstock diet have been identified as major dietary factors that determine successful reproduction and survival of offspring. Some fish species readily incorporate dietary unsaturated fat ty acids into eggs, even during the course of the spawning season. Highly u nsaturated fatty acids (HUFA) with 20 or more carbon atoms affect, directly or through their metabolites, fish maturation and steroidogenesis. In some species, HUFA in broodstock diets increases fecundity, fertilization and e gg quality. As in higher vertebrates, vitamin E deficiency affects reproduc tive performance, causing immature gonads and lower hatching rate and survi val of offspring. For example, elevation of dietary alpha -tocopherol level s has been found to reduce the percentage of abnormal eggs and increase fec undity in the gilthead seabream (Sparus aurata). Ascorbic acid has also bee n shown to play an important role in salmonid reproduction, where the dieta ry requirement of broodstock was higher than that of juveniles. Among diffe rent feed ingredients, cuttlefish, squid and krill meals are recognized as valuable components of broodstock diets. The protein component of cuttlefis h and squid together with their optimal concentration of HUFA appear to be responsible for their positive effect on reproductive performance. Both pol ar and nonpolar lipid fractions of raw krill were found to effectively impr ove egg quality. (C) 2001 Published by Elsevier Science B.V.