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:).bO'b 6Dlo\ ,e..t ( \ , -. 'lahamense var. compressa ific red tides. Phycologia .dministration), Center for ition. 2001. Natural toxins. Ties products, hazards, and ion. U.S. Public Health . The annual toxicological ffers, T akifugu niphobles kifugu alboplumbeus (Ri- ong Kong coastal waters. )SU, and Y. Onoue. ]997. ish poison in Bangladeshi ;(3):423-431. Transactions of the American Fi,\'heries Sociery 137:1327-]334, 2008 @ Copyright by the American Fisheries Society 2008 DOl: 1O.1577{f07.192.1 q~9S [Note] Genetic Effective Size in Populations of Hatchery-Raised Red Drum Released for Stock Enhancement JOHN R. GOLD, * LIANG MA, AND ERIC SAILLANT Cemerfor Biosystematics and Biodiversity, Texas A&M University, College Station, Texas 77843-2258, USA PAUL S. SILVA AND R. R. VEGA Texas Parks and Wildlife Department, Coastal Conservation Associationl Central Power and Light Marine Development Center, Flour Bluff, Texas 78418, USA Abstract.-Genetic analysis of progeny from 13 spawning events occurring over a 2-week period in a Texas Parks and Wildlife Department (TPWD) hatchery for red drum Sciae- nops ocellatus during the spring of 2002 and hatchery spawning and release records over the 2003 spawning season were used to estimate the average genetic effective size of an average spawn and an average hatchery-released population. The purpose of this study was to assess the potential for a Ryman-Laikre effect in the TPWD red drum stock enhance- ment program. Genetic analysis revealed that 16 of 27 dams (59.2%) and 16 of 18 sires (88.9%) spawned at least once. The average effective size (Ne) for a single spawn was 2.59, approximately 43% less than the maximum Ne (4.55) predicted if all possible mating (dam X sire) combinations had occurred and family size per mating combination had been equivalent. The reduction in Ne stemming from the actual number of mating combinations was approximately 34% and appeared to be due primarily to nonspawning dams; the reduction in Ne generated by the actual variation in family size was approximately 9%. Spawning and release records at the TPWD hatchery indicate that in 2003 the number of released populations per bay or estuary ranged from 7 to 27. Using the average effective size (N) estimate for a single spawn (2.59), the estimated average effective size of all released fish per bay or estuary (NeR) in 2003 ranged from about 28.5 to about 46.6. These values of NeR are less than the averages estimates of about 272 and 263 for the long-term (N) and contempora- neous (NeV) effective size, respectively, of red drum in bays and estuaries in the northern Gulf of Mexico and indicate a reasonable potential for a Ryman-Laikre effect. Approaches that might be employed to increase the N eR of TPWD-re]eased fish and decrease the probability of a Ryman-Laikre effect are discussed. Hatchery-reared fish used in stock enhancement are often produced by a small number of breeders relative to the hypothesized number of breeders in natural populations (Ryman and Laikre 1991). Consequently, a small numher of hroorHi<h m~" rnnt~a..".~ ,,,"______ juvenile pool, thereby increasing significantly the variance in family size in the overall population. This can lead to a reduction in the genetic effective size (N) of the wild population (Ryman and Laikre 1991; Tringali and Bert 1998) and result in inbreeding, an accumulation of deleterious genotypes, and a reduction in fitness within the fishery (Frankham 1995; Higgins and Lynch 2001). The negative aspects, of course, are based on the assumption that the hatchery-released or "stocked" fish reproduce and contribute significantly to subsequent wild generations (Ryman and Laikre 1991). This potential reduction in effective size of the wild population has been termed the Ryman-Laikre effect (Tringali and Bert 1998). In this paper, we present the results of a study on the effective size of a "simulated" release population of red drum Sciaenops ocellatus. Briefly, in response to substantial declines in red drum abundance and recruitment, the Texas Parks and Wildlife Department (TPWD) implemented in the 1980s a stock enhance- ment program that now supports the wild fishery in Texas waters through annual releases of hatchery- produced red drum fingerlings (McEachron et al. '1995). At present, the program releases between 20 and 30 million hatchery-raised fingerlings annually into eight different Texas bays and estuaries (Vega et al. 2003) and represents one of the most visible (certainly the largest) marine stock enhancement program in the country. To ensure the maintenance of wild genotypes among released fish and maximize genetic diversity, the TPWD program utilizes randomly sampled adult fish from the wild as broodstock and replaces at least 25% of the broodfish (both sexes) each year (McEachron et al. 1995). In addition, both dams and sires are alternated among spawning tanks (typically three dams and two sires n~r t;mk) "rrn<<