WOLCOTT, D.L.; WOLCOTT, T.G.; No. Carolina State Univ., Raleigh; No. Carolina State Univ., Raleigh: Potential fecundity of female blue crabs, Callinectes sapidus

Blue crabs are susceptible to sperm limitation because females mate during one brief interval at their molt to maturity and then rely on stored sperm for production of multiple broods. Sperm limitation has been documented in laboratory studies and under certain field conditions (regions of heavy fishing pressure or high incidences of mating). We undertook a field study to determine whether sperm limitation is detectable in the female crabs that are spawning in North Carolina. We sampled females near five NC inlets in multiple months and assayed brood size, fertility and sperm stores to determine whether females were running out of sperm while still able to produce broods. While brood fertility did vary with season (higher rates of infertility in March than in August), the mean rate of infertility in other months did not exceed 2%. Nearly all females had sufficient sperm stored to produce at least one additional full brood (94%, n=48). Brood size did not vary between sites or months (range of averages 2.3-4.0 X 106 eggs/brood, n = 8 sample averages). If females with depleted sperm stores cease brood production, we would not expect to see broods with high incidences of infertile eggs, or be able to detect sperm limitation by confining our analysis to females with broods. Therefore, we also sampled non-brooding females, and these also had ample stored sperm. The large size of average broods, low rates of infertility, and the presence of stored sperm are all inconsistent with sperm depletion, and sperm limitation did not appear to be occurring in the NC population of blue crabs during the 2002-3 spawning seasons. We note numbers of very small mature females (carapace width <80mm) that are not subject to the fishery, but that have mated and are successfully reproducing.