Production of second generation penaeid shrimp,Penaeus stylirostris,from Mexico

The life cycle of the penaeid shrimp, Penaeus stylirostris, was completed in captivity with the production of F₂ generation nauplii. Over one million F₂ generation nauplii were harvested from the F₁ generation represented by laboratory-reared adult shrimp. The studies were completed in a laboratory simulated, tropical environment for maturation and spawning, and in pond systems located in a temperate environment for growout of the F₁ generation.     

Genetics of Body Color in Tilapia mossambica

Gold, bronze, and black (normal pigmentation) body colors in Tilapia mossambica are controlled by a single autosomal gene with incomplete dominant gene action: GG fish are black gg fish are gold; Gg fish are bronze. Because gold body color is produced by the recessive genotype, it is easy to produce and to maintain a truebreeding population of gold T. mossambica for commercial purposes. If all other colors are culled, the population will breed true, because gold × gold will always produce 100% gold offspring. The G gene will be a valuable genetic marker for many genetic studies, such as the production of gynogenetic T. mossambica .     

Production of the Endangered Rio Grande Silvery Minnow,Hybognathus amarus,in the Conservation Rearing Facility at the Los Lunas Silvery Minnow Refugium

This article describes the initial season‐long yield trial of raising the endangered Rio Grande silvery minnow, Hybognathus amarus, in the conservation rearing facility at the Los Lunas Silvery Minnow Refugium. Ten thousand fish (90,900/ha) were stocked on June 22, 2010. Production was based on a total of 653 mL (5.936 L/ha) of 11‐37‐0 N‐P‐K and 5.5 kg (50 kg/ha) of alfalfa pellets. Fish were harvested in October; almost all were harvested 18–27 October. At stocking, fish averaged 21.7 mm total length and mean weight was 0.10 g. At harvest, fish averaged 48.98 mm and 1.12 g. Fish were sampled monthly, and increased lengths and weights through the study were significant (P = 0.05). Five thousand eight hundred ninety‐two fish were harvested (58.92% survival). Yield was 59.99 kg/ha. Temperature, dissolved oxygen (DO), pH, un‐ionized ammonia, nitrite, turbidity, alkalinity, and chloride were measured at seven sites throughout the outdoor refugium. Secchi disc visibility was measured in the stream and in the ponds. Only two variables (DO and pH) went outside permitted values, but were easily corrected. Harvest was difficult due to the many different naturalized areas consisting of varying depths, channel widths, and substrates.     

Golden Shiner Notemigonus crysoleucas× Rudd Scardinius erythrophthalmus Hybrids: Gonad Histology and Spawning Trials

Hybrid fish were produced in ponds by crossing golden shiners × rudd ( Notemigonus crysoleucas × Scardinius erythrophthalmus ) and rudd × golden shiners. Histologically, testes from the hybrids contained spermatocytes that resembled those of the parental species, but no sperm were observed. Lack of sperm in hybrids could have been a seasonal effect. The ovaries of both types of hybrids contained variable numbers of morphologically normal, vitellogenic oocytes and numerous abnormal oocytes in the chromatin nucleolar stage. Abnormal oocytes were necrotic or had irregularly shaped nuclei and clumped chromatin. Many oocyte nests contained infiltrating macrophnges. Spawning trials with F₁ hybrids did not result in spawning behavior or production of F₂ generation fish. Colden shiner × rudd hybrids are of reduced fecundity, but sterility was not conclusively demonstrated.     

Effects of Intraspecific Hybridization in Tilapia nilotica on Survival Under Ambient Winter Temperature in Alabama

Viability under ambient winter temperatures in Alabama was assessed for Auburn University-Egypt and Auburn University-Ivory Coast strains of Tilapia nilotica and their F₁, F₂, and four backcross hybrids. Egypt strain was more viable ( P = 0.05) than Ivory Coast strain. Observed mean viabilities of the F₁ hybrids were intermediate between those of the parental strains. Viabilities of the reciprocal F₁ hybrids were not significantly different. Viabilities of the reciprocal F₂ hybrids were not significantly different. Backcross hybrids that were produced by crossing F₁ hybrid females to Egypt strain had a greater observed mean viability than those that were produced by crossing F₁ hybrid females to Ivory Coast strain. Average viabilities of the parental strains, F₁, F₂, and backcross hybrids were not significantly different. Heterosis in F₁, F₂, and backcross hybrids was −1.39%,−0.82%, and −2.08%, respectively. Viability under ambient winter temperatures in Alabama in T. nilotica appears to be controlled by additive rather than by dominance effects, which means that selection rather than crossbreeding is the breeding technique that should be evaluated to improve this trait in T. nilotica .     

Estimates of Additive Genetic Effects, Maternal Genetic Effects, Individual Heterosis, Maternal Heterosis, and Egg Cytoplasmic Effects for Growth in Tilapia nilotica

Lengths and weights of Auburn University-Egypt and Auburn University-Ivory Coast strains of Tilapia nilotica and their F₁ F₂, and backcross hybrids were analyzed by multiple regression to estimate strain additive genetic effects, strain maternal genetic effects, individual heterosis (specific combining ability), maternal heterosis, and strain egg cytoplasmic effects for growth to determine why heterosis of the F₂ and backcross hybrids was greater than that of the F_I hybrids. Individual heterosis and maternal heterosis made the greatest contributions to growth. The F₂ and backcross hybrids were larger than the F₁ hybrids because of maternal heterosis. Regression coefficients were used to predict growth for any possible hybrid combination. Egypt ♀× Ivory Coast ♂ F_I hybrid females backcrossed to Egypt males and Egypt ♀× Ivory Coast ♂ F₂ hybrids were the largest groups evaluated in this study and were also predicted to have faster growth rates than any other possible Egypt-Ivory Coast hybrid.