Analyses of gonadal cycling by oyster broodstock, Crassostrea virginica (Gmelin), in Louisiana

Oysters held near-shore in Caminada Bay, Louisiana during the summer, exhibit hypertrophic gonads with prominent genital canals beneath transparent mantle tissue about four weeks post-hatchery spawning, indicating recycling. Broodstock (N = 200) were analyzed histologically over a two-year period to document such gametogenesis, using Gonad/Body Ratios (GBR) and developmental stages. Ten oysters were randomly selected from a broodstock pool prior to each spawning attempt, and monthly during the winter-spring. As expected, the mean GBR before successful spawning attempts was significantly greater (P less than or equal to 0.05) than the mean GBR before unsuccessful attempts. A dramatic drop in the percent occurrence of the advanced spawning and regression stage from May to June, a >40% spawning stage occurrence from May to October, and fluctuations in the percent occurrence of early and late developmental stages during the summer months illustrates gonadal recycling.