This study was designed to evaluate the e¡ects of dietary supplementation with brewers yeast (Brewtech s ) and nucleotides (Optimu" n), either singularly or in combination, on red drum growth, body composition, stress responses and possible resistance to Amyloodinium ocellatum infection. Juvenile red drum ( $ 1g initially) fed practical ¢sh-meal-based diets for 6 weeks had similar weight gain regardless of whether the diet was unsupplemented (basal) or supplemented with brewers yeast (2% of diet), nucleotides (Optimu" n at 0.2% of diet) or both brewers yeast (2% of diet) and nucleotides (Optimu" n at 0.2% of diet). Dietary e¡ects on hepatosomatic index, intraperitoneal fat ratio or whole-body composition were not signi¢cant, except that ¢sh fed the singular nucleotide supplement had a signi¢cantly higher wholebody lipid content compared with ¢sh fed the basal diet. No signi¢cant dietary e¡ects on cortisol response were observed after a 15 min con¢nement stress test perhaps because of the extreme variation among individual ¢sh. Subsequently, in situ challenge by co-habitation with A. ocellatum caused 100% mortality regardless of dietary treatment within a 48 h period. It is concluded that dietary supplementation of brewers yeast and nucleotides did not promote enhanced growth or improved cortisol response and resistance to uncontrolled amyloodiniosis in juvenile red drum, at least at the tested dosages.

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 Sciaenops 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 enhancement 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 (N e ) for a single spawn was 2.59, approximately 43% less than the maximum N e (4.55) predicted if all possible mating (dam 3 sire) combinations had occurred and family size per mating combination had been equivalent. The reduction in N e stemming from the actual number of mating combinations was approximately 34% and appeared to be due primarily to nonspawning dams; the reduction in N e 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 e ) estimate for a single spawn (2.59), the estimated average effective size of all released fish per bay or estuary (N eR ) in 2003 ranged from about 28.5 to about 46.6. These values of N eR are less than the averages estimates of about 272 and 263 for the long-term (N eI ) and contemporaneous (N eV ) 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-released fish and decrease the probability of a Ryman-Laikre effect are discussed.

The stock enhancement program for red drum Sciaenops ocellatus in Texas annually releases from 25 to 30 million fingerlings into Texas bays and estuaries and represents one of the largest such programs for marine fishes worldwide. We used 16 nuclear-encoded microsatellites and a 370-base-pair fragment of the mitochondrial DNA (mtDNA) D-loop to assign red drum sampled from two bays along the Texas coast to either hatchery or wild origin. A total of 30 hatchery-released fish were identified among 321 red drum belonging to three year-classes sampled from Galveston Bay, while a total of 11 hatchery-released fish were identified among 970 red drum belonging to four year-classes sampled from Aransas Bay. Allelic richness (microsatellites) was significantly lower among hatchery-released fish than among hatchery broodfish and wild fish. Similarly, the expected number of mtDNA haplotypes in hatchery-released fish (based on simulation analysis) was significantly lower than that expected in a random sample of both brood and wild fish. The contribution of brood dams, sires, and dam 3 sire combinations to the hatchery-released fish was nonrandom, as was the distribution of hatchery-released and wild fish with respect to sampling stations (localities) within each bay. The possibility of a Ryman-Laikre effect is discussed.

233 234 W. H. Neill et al.Ecophys.Fish is a quantitatively explicit interpretation of concepts originally formalized by F.E.J. Fry, almost 60 years ago. Fry's "physiological classification of environment" and his concept of "metabolic scope for activity" were coupled with conventional bioenergetics to provide the model's theoretical basis. The model's inputs are initial size of fish, and time series of temperature, pH, dissolved-oxygen concentration (DO), salinity, and food availability and its energy content. Outputs are food consumption, oxygen consumption, waste production, energy content of fish biomass, and growth. Indirectly, the output is a measure of relative fitness of the fish-environment system to support fish growth.Two variants of the model represent the euryhaline red drum (Sciaenops ocellatus) and the freshwater bluegill (Lepomis macrochirus). Ecophys.Fish had its beginnings in laboratory experiments with juvenile red drum. These experiments enabled definition of functions and their parameterization, leading to a working model that effectively simulated growth of red drum in various pond and estuary trials with caged fish. Subsequently, Ecophys.Fish was converted to simulate growth rates of caged bluegill involved in stream ecoassays. The latter work confirmed the model's generality and the utility of automated routine respirometry for empirically estimating a key model parameter.Ecophys.Fish comprises an effective tool for resolving sources of variation in fish growth, even in natural systems with high levels of environmental variability. Moreover, the model has utility for probing biological and ecological mechanisms underlying fish growth and production. Finally, Ecophys.Fish is capable of producing rich hypotheses, e.g., 1) the optimum temperature for growth decreases whenever DO, food availability, or energy density of available food is limiting; 2) with unlimited DO and food availability, the optimum temperature for growth increases with increasing fish size but only when energy density of food is limiting; and, 3) when neither availability nor energy density of food is limiting, growth can be much faster under diel-cycling regimes of temperature and DO than under the optimum constant temperature/DO regime. Under Ecophys.Fish, environmental regimes that are best for survival are not necessarily those that are best for growth.

Parentage analysis, employing five hypervariable microsatellite markers, was used to follow spawning patterns of red drum Sciaenops ocellatus broodfish in two spawning tanks through most of a calendar year in a marine fish hatchery dedicated to stock enhancement. Five of six dams and all four sires spawned at least once during the year. Variation in dam and sire spawning incidence and in number of progeny produced per dam and per sire translated into reduced genetic effective size (N e) per spawn by 40·6% in one tank and 50·8% in the other.