DIFFERENCES IN GROWTH, MORPHOMETRIC TRAITS, AND MALE SEXUAL MATURITY AMONG PACIFIC WHITE SHRIMP, PENAEUS-VANNAMEI, FROM DIFFERENT COMMERCIAL HATCHERIES

Postlarvae of Penaeus vannamei from four commercial hatcheries (lots) were divided between two laboratory sites. Body length, body weight, condition factor, male sexual maturity, and ratios of the tail length and carapace width to body length, were monitored at days 50, 80, 110, 170, 200, 230 and 270. There were small differences in body size between sexes within each lot at all age groups. Consistent differences were observed between sexes in the proportional variables for all age groups and sites. Males had a larger average tail length ratio than females, while females had a larger average carapace width ratio and higher average condition factor than males. Average tail length ratio of younger age groups was smaller and the average condition factor was lower than those of the older groups. Significant differences in all of the morphometric traits were found between sites, indicating that the environmental differences affected not only the growth but also the shape of the shrimp. Rank order of the lots for all of the morphometric traits varied among age groups and between sites. However, certain lots consistently exhibited significantly smaller values fo the proportional variables than other lots, independent of age and site. Percent of maturing males was significantly different among lots, and the rank order was consistent for ages and sites. These results suggest the presence of genetic differences for morphometric traits and male sexual maturity among the shrimp hatchery lots, although the traits are largely affected by environmental variance.