54 March 2012 Major improvements include separation of male and female adult flounder during the offseason, growing large female broodstock in captivity, and spawning and rearing eggs and larvae at 18 °C. Acknowledgments This work was supported by contributions from the Sid W. Richardson Foundation, USDACSREES, and the Coastal Conservation Association of Texas. The University of Texas at Austin Institutional Animal Care and Use Committee has approved the use of vertebrate animals as described in this work under UT IACUC Protocol # AUP-2010-00049. This is contribution number 1617 of the UT Marine Science Institute. References Arnold, C.R., W.H. Bailey, T.D. Williams, A. Johnson and J.L. Lasswell. 1977. Laboratory spawning and larval rearing of red drum and southern flounder. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 31:437-440. Blandon, I.R., R. Ward, T.L. King, W.J. Karel and J.P. Monaghan, Jr. 2001. Preliminary genetic population structure of southern flounder, Paralichthys lethostigma, along the Atlantic Coast and Gulf of Mexico. Fishery Bulletin 99:671-678. Daniels, H., W.O. Watanabe, R. Murashige, T. Losordo and C. Dumas. 2010. Culture of southern flounder. Pages 82-100 In H.V. Daniels and W.O. Watanabe, editors. Practical Flatfish Culture and Stock Enhancement. Wiley-Blackwell, Hoboken, New Jersey, USA. Faulk, C.K. and G.J. Holt. 2009. Early weaning of southern flounder, Paralichthys lethostigma, larvae and ontogeny of selected digestive enzymes. Aquaculture 296:213-218. Froeschke, B.F., B. Sterba-Boatwright and G.W. Stunz. 2010. Assessing southern flounder (Paralichthys lethostigma) long-term population trends in the northern Gulf of Mexico using time series analyses. Fisheries Research 108:291-298. Luckenbach, J.A., R.J. Borski, H.V. Daniels and J. Godwin. 2009. Sex determination in flatfishes: mechanisms and environmental influences. Seminars in Cell and Developmental Biology 20:256-263. Montalvo, A.J. 2011. Sex determination in southern flounder, Paralichthys lethostigma, from the Texas Gulf Coast and implications of climate change. Thesis. The University of Texas at Austin, Austin, Texas, USA. Reichers, R. 2008. Regulations Committee Southern Flounder Update, Texas Parks and Wildlife Department Regulation Committee, Houston, TX, http://www.tpwd.state.tx.us/business/ feedback/meetings/2009/1106/transcripts/regulations.committee/index.phtml. Smith, T.I.J., D.C. McVey, W.E. Jenkins, M.R. Denson, L.D. Hewyard, C.V. Sullivan and D.L. Berlinsky. 1999. Broodstock management and spawning of southern flounder, Paralichthys lethostigma. Aquaculture 176:87-99. van Maaren, C.C. and H.V. Daniels. 2001. Effects of temperature on egg hatch, larval growth and metamorphosis for hatcherycultured southern flounder, Paralichthys lethostigma. Journal of Applied Aquaculture 11:21-33. Watanabe, W.O., C.A. Woolridge and H.V. Daniels. 2006. Progress toward year-round spawning of southern flounder broodstock by manipulation of temperature and photoperiod. Journal of the World Aquaculture Society 37:256-272. Table 2. Standard length (mm) and survival (% from hatch) of southern flounder larvae reared in various temperatures. Trial Stage Temperature (°C) Survival (%) Standard length (mm) 1 1 24 0.4 ± 0.4 a 4.9 ± 0.7 a 21 3.0 ± 2.4 a 5.7 ± 0.4 ab 18 32.3 ± 9.9 b 6.3 ± 0.1 b 2 1 18 18.2 ± 1.0 a 5.5 ± 0.1 a 15 7.2 ± 2.2 b 4.1 ± 0.1 b 12 No survival -------- 1 2 24 71.3 ± 9.4 a 7.1 ± 0.5 21 83.7 ± 10.4 ab 7.2 ± 0.2 18 87.5 ± 6.5 b 7.4 ± 0.2 2 2 18 66.7 ± 3.8 a 7.3 ± 0.3 a 15 71.7 ± 6.3 a 7.3 ± 0.3 a 12 46.0 ± 4.6 b 5.8 ± 0.5 b Table 3. Standard length (mm) and survival (% from hatch) of southern flounder larvae. Temperature (°C) Survival (%) Standard length (mm) 24 3.4 ± 2.2 a 5.1 ± 0.2 21 3.6 ± 3.2 a 5.3 ± 0.2 18 19.8 ± 8.7 b 5.9 ± 0.5 rear southern flounder larvae along the Atlantic coast (2123 °C). Sex determination in southern flounder from both areas is sensitive to rearing temperature. Genetic males (XY) always develop into phenotypic males, but genetic females (XX) may differentiate into phenotypic males or females, depending on juvenile rearing temperatures. Recent studies suggest that there are differences in the effects of temperature on sex determination between the two populations. The water temperature that results in a 1:1 sex ratio is 23 °C in Atlantic coast fish (Luckenbach et al. 2009) but 18 °C in Texas fish (Montalvo 2011). Differences in the optimal rearing temperatures between Atlantic and western Gulf of Mexico fish may be a result of genetic differences between populations and/or adaptation to local environmental conditions (Luckenbach et al. 2009). Outlook Collaboration with various state hatchery facilities is ongoing, with the objective of developing large-scale southern flounder production, either for aquaculture or stock enhancement. Southern flounder research at FAML has been progressing steadily over the past several years with improvements in egg production, larval rearing, and juvenile stages. (Continued from page52)
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