Growth of Postsettlement Juveniles of the Florida Stone Crab, Menippe Mercenaria (Say) (Decapoda: Xanthidae), in the Laboratory

We combined relevant data from three laboratory studies to define molt increment and intermolt period of post settlement (<10.5-mm carapace width [CW]) juveniles of the Florida stone crab, Menippe mercenaria. Regression of postmolt CW on premolt CW yielded a linear relationship. Mean growth (proportional increase in CW) per molt was 18%, but variation among individuals was high. Molt increment increased significantly and linearly as size of the crab increased. Intermolt period increased significantly with increasing crab size in a log-linear relationship. We attempted to define biologically meaningful size classes (instars) by using mean size-at-instar of individuals raised from the megalopal stage and size-at-molt of individuals who completed eight or more molts in the laboratory. Three determinants (mean, median, and maximum of intermolt period) and two techniques (one based on observed complete intermolt periods and one based on estimates of intermolt period) were used to predict age-at-size of instar-12 juveniles (>10.4 mm CW). Within a size class, estimates of mean, median, and maximum intermolt periods generally were not significantly different from corresponding values for the three determinants calculated using the observed intermolt periods. However, summing the size-specific intermolt period values to calculate age resulted in disparities among the six estimates of age at the end of instar 11. Nevertheless, our analyses suggest that under normal salinity and temperature conditions in Florida, postsettlement juvenile M. mercenaria may require up to 12 months to complete growth to approximately 10 mm CW.