Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: 11/24/2003
Publication Date: 2/20/2004
Citation: Riley, K., Riche, M.A., Davis, M. 2004. Sustained tank spawning of southern flounder fed a practical broodstock diet. Book of Abstracts Aquaculture America. Abstract, addendum. p.17. Interpretive Summary:
Technical Abstract: The euryhaline southern flounder, Paralichthys lethostigma, is tolerant of a wide range of temperatures and salinities, making this species an ideal candidate for aquaculture. Some research methods and culture protocols have been developed for southern flounder; however, a bottleneck exists in the production of high quality gametes and larvae. Currently, too few fingerlings are being produced to galvanize the sustainable development of commercial grow-out operations. Research currently being conducted at Harbor Branch Oceanographic Institution is focused on developing year-round spawning methods and advancing hatchery techniques for this species. The objectives of this study were to evaluate gamete and larval quality for spawns collected from natural and hormone-induced tank spawning of fish fed a diet of thawed fish or a practical growout diet. Southern flounder were distributed between two recirculating aquaculture systems (20 m3) during the summer of 2002. Each system was stocked with 20 wild-caught females and 15 hatchery-reared males. Broodstock were fed daily a diet of thawed fish including Atlantic silversides, Menidia menidia, Spanish sardines, Sardinella aurita, and Anchovies, Anchoa spp. After acclimation (30 - 45 d), broodstock in one system were offered a commercially produced 7-mm floating pelleted diet while the other fish remained on the thawed fish diet. Both systems were fed daily to satiation or 0.25% bodyweight per day. The recirculating systems were maintained under a natural photoperiod with temperature control (Fig. 1). After 87 d, 2 spawns were collected from the broodstock fed thawed fish. The spawns were small (n = 26,000 eggs) with low fertilization (<1%). After sampling fish from both systems and observing ripe eggs and flowing milt, all fish were implanted with a 75-µg slow-release pellet of gonadotropin-releasing hormone analogue (27.5 - 91.7 µg GNRH-a/kg body weight). Approximately 72 h following implantation, fertilized eggs were collected from each system. Twenty spawns were collected from broodstock fed thawed fish. Egg production ranged from 6,000 to 181,000 eggs and fertilization rates were 44 ± 38%. Seventeen spawns were collected from the broodstock fed the commercial diet. Egg production ranged from 9,000 to 188,000 eggs and fertilization rates were 42 ± 38%. The same broodstock are being conditioned to spawn in 2003-2004 to evaluate fertilization success, egg quality and biochemistry, and larval survival.