The 2nd Generation of Improved Lines and Mapping Fish of Yellow Perch has been Produced by OARDIP

Bluegill (Lepomis macrochirus) monosex culture holds considerable potential as a method to improve bluegill aquaculture production as males grow much faster than females. A detailed understanding of the time of gonadal development and differentiation is critical to control sex and optimize culture. In the present study, we systematically studied gonadal sex differentiation of the bluegill sunfish and its relation to fish size and age from hatching to 90 days post hatching (dph) using a slow-growing batch (SGB) and a fast-growing batch (FGB) of fish. The results indicated that the gonadal differentiation in bluegill was more related to body size than to age. In presumptive ovaries, germinal and somatic differentiation began between 13.2 and 16.0 mm (60 dph in SGB and 30 dph in FGB) in total length (TL). The outgrowths from the proximal and distal portions of the gonads and the fusion of the outgrowths to form the ovarian cavity occurred between 16.0 and 21.0 mm TL (80 dph in SGB and 50 dph in FGB) with germ cells undergoing meiosis. The gonads in the females larger than 25.5 mm TL always had peri-nucleolus oocytes. In presumptive testes, the efferent duct formed in the fish ranging from 25.4 to 28.0 mm TL (90 dph in SGB and 70 dph in FGB) with the onset of meiosis and testes contained spermatocytes exhibiting active meiosis in males larger than 33.0 mm TL. These findings indicate that bluegill is a differentiated gonochorist and sex differentiation occurs earlier in females than males. Based on our results, we suggest that the critical period of sex differentiation in bluegill occur between 13.2 and 16.0 mm TL and histological sex differentiation is distinguishable in most fish larger than 21.0 mm TL. Aquaculture (2009), 294: 138–146. doi:10.1016/j.aquaculture.2009.05.024 Evaluation of relative growth performance and genotype by environment effects for cross-bred yellow perch families reared in communal ponds using DNA parentage analyses Han-PingWang, Li Li, Geoff Wallat, Bonnie Brown, HongYao, Zexia Gao, Laura Tiu, Paul O’Bryant, Dean Rapp & Russ MacDonald Abstract From 24 mating sets, 6300 fingerlings of yellow perch (Perca flavescens) were stocked into one pond and equal numbers of progeny from six representative sets out of the 24 were stocked into each of two other ponds.From 24 mating sets, 6300 fingerlings of yellow perch (Perca flavescens) were stocked into one pond and equal numbers of progeny from six representative sets out of the 24 were stocked into each of two other ponds. After communal rearing for 21 months, total length and body weight were assessed for n=300 fish in each of the three ponds and molecular pedigrees were performed for each sampled individual to assign the progeny back to the original parents. The overall average number of alleles per locus was A = 16.4 and observed and expected heterozygosities were Ho=0.88 and He=0.77, respectively. The mean weight of random samples and the top 10% fast-growing fish from the pond with all sets was significantly greater than those from either of the two replicate ponds with six crosses. For the two replicate ponds, no significant differences were found in family rankings and assignment of the top 10% heaviest fish, indicating that families with superior growth performance in one pond also exhibited the same superior growth performance in the replicate pond. However, there were no significant correlations detected in family mean weights of the top 10% fish between any two of the three ponds. Aquaculture Research (2009), doi:10.1111/j.13652109.2009.02232.x