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Besides some mammals and a few model organisms, the presence of genetic variation in ovary or gonad development at ages before that of reproduction has not been established for marine oviparous species nor has the correlation with reproductive traits at maturity. In this investigation, ovary development was evaluated for genetic variability in a full-sib family structured population of subadult shrimp. The numbers of each oocyte type that were present were counted, measured, and used to evaluate the following traits: total oocyte number, mean oocytes diameter, and ovary maturity (OM). The total ovary area was also measured for each female. Genetic variation was assessed through the estimation of the parameter 'heritability'. The heritability ([h.sup.2]) of total number of oocytes was zero, but large heritability values were seen for mean oocytes diameter ([h.sup.2] = 0.57 [+ or -] 0.27) and OM ([h.sup.2] = 0.71 [+ or -] 0.26). Family means correlations between traits in subadults with traits measured in their full-sibs when adults (days to first spawn, total number of spawns, total fecundity, and fecundity at first spawn) indicated the existence of some significant associations between reproductive traits at the two ages. These findings point toward an early genetic determination of reproductive capacity in this crustacean., Introduction Reproductive traits at maturity have been previously demonstrated to have significant genetic variation in animals. For example, among mammals, litter size, ovulation rate, and uterine capacity have been the [...]