Life-History Aspects of Stone Crabs (Genus Menippe): Size at Maturity, Growth, and Age

Abstract

Knowing important aspects of life history, such as size at sexual maturity, growth rate, and size at age, is critical for understanding species' population dynamics. For harvested organisms, these life-history characteristics are important in assessing the efficacy of fishery regulations. We used a 15-year database on stone crabs (genus Menippe) inhabiting west-central Florida waters to estimate these life-history aspects. Transition points in crusher-claw propodus length (PL):CW allometry and discriminant function analysis indicated that 50% morphological maturity (CW50) occurred at approximately 70 mm CW for males and 60 mm CW for females. Patterns in the proportions of physiologically mature (gravid) and functionally mature (ovigerous) females in 10-mm-CW size-classes followed the female morphological maturity pattern. The CW50 was significantly smaller than the mean size at behavioral maturity (participation in mating) in males (86 mm CW), but was not in females (62 mm CW). In both sexes, PL:CW allometry also shifted at 30-35 mm CW, allowing us to define three life stages: small juvenile, large juvenile, and adult. Male PL:CW allometry increased dramatically in adulthood, whereas adult-female PL:CW allometry remained the same as that of large juvenile females. Molt frequency decreased with increasing size in both sexes; molt increment increased with increasing size in males but increased only up to CW50 in females. Adult males and females molt annually in cycles dictated by female reproduction. Males enter the commercial fishery during age three and females during age four. Females have contributed to the reproductive population prior to entering the fishery, but most males probably have not.