Assessment of Maturity in the Eastern Gulf of Mexico Florida Stone Crab Menippe mercenaria Fishery

Abstract

AbstractThe Florida stone crab Menippe mercenaria supports one of Florida's most valuable commercial fisheries. Sustained fishing pressure and overexploitation, despite negative trends in landings, have facilitated the need to transition from stock assessments based on effort and landings toward more sophisticated methods. This requires accurate knowledge of life history parameters, such as size at sexual maturity. The physiological, behavioral, and functional maturity of female Florida stone crabs and the physiological maturity of male crabs were assessed in individuals collected throughout the geographically fished range of the population between 2013 and 2014. Morphological maturity of both sexes was assessed in individuals collected from the same locations in 2005–2016. Histology was used to determine oocyte maturity, presence of spermatophores, and presence of postovulatory follicles in females and the production of spermatophores (present in the anterior vas deferens) in males. Decision tree analysis determined that 50% of females were mature at 43 mm carapace width (CW) based on an indicator of physiological and behavioral sexual maturity. In males, physiological maturity occurred at a CW of 34.75 mm. Sexual maturity estimated using morphological maturity occurred at 66.3 mm CW in females and 63.1 mm CW in males. Differences in estimated size at sexual maturity between morphological maturity and physiological, behavioral, and functional maturity indicate that the relative growth of body parts is not reliable for estimating sexual maturity in Florida stone crabs. Smaller females may be contributing more to the spawning population than had been previously estimated. Large, morphometrically mature males may be more successful in mating encounters, but during times of flux in population size structure (i.e., fewer large males), morphologically immature but physiologically mature males have increased mating opportunities. Results indicate that male and female Florida stone crabs can contribute to the reproductive population multiple times before they become vulnerable to the fishery.