|Van wyk, Peter|
Submitted to: Book of Abstracts World Aquaculture Society
Publication Type: Abstract only
Publication Acceptance Date: 12/1/2001
Publication Date: 1/27/2002
Citation: VAN WYK, P.M., RICHE, M.A., BENETTI, D.D. CONDITIONING AND INDUCED SPAWNING OF CAPTIVE-REARED SOUTHERN FLOUNDER PARALICHTHYS LETHOSTIGMA. BOOK OF ABSTRACTS WORLD AQUACULTURE SOCIETY. 2002. p.346. Interpretive Summary:
Technical Abstract: The southern flounder, Paralichthys lethostigma, is a valued food fish that has received attention in recent years as a candidate for commercial culture. Reliable methods for controlled breeding and production are needed for development of an industry based on this species. Several researchers have demonstrated that flounder broodstock collected from the wild can be induced to spawn in captivity under controlled conditions. However, if this species is to become truly domesticated, the life cycle must be closed. Closing the life cycle will also eliminate the uncertainties associated with collection of wild broodstock. The culture technology must be developed to the point where a reliable source of seedstock for each succeeding generation can be produced by captive-reared broodstock.. Southern flounder juveniles spawned from wild broodstock in December 1999 at Harbor Branch Oceanographic Institution were reared for 3 years at low densities (<20 fish/m3) in recirculating production systems at salinities ranging from 0 - 32 ppt. Spawning trials were initiated with a select group of these fish as they approached the age at which wild southern flounder typically achieve sexual maturity. In August 2001, three months prior to the start of the southern flounder spawning season, 30 of the largest females and males (sex ratio = 1:1) were selected and transferred to a 20-mt broodstock conditioning tank. Over the next three months temperatures were gradually lowered from 26oC to 16oC, the threshold temperature at which spawning activity is triggered. The conditioning tank was shaded to maintain low light intensity, with a natural photoperiod. The captive-reared broodstock were fed a diet consisting of frozen silversides, squid, shrimp, and a formulated maturation diet. Fish were sampled to check for gonadal development when initially transferred into the conditioning system and again in late November, at the beginning of the spawning season. After the second gonad sampling event, female broodstock were implanted with Gn-RH-a, while males were injected with HCG. Data collected included egg production, fertilization rates, hatching rates, and survival to metamorphosis. Results of these spawning trials are reported and compared to results obtained with wild broodstock.