Factors Influencing Refuge Occupation by Stone Crab Menippe Adina Juveniles in Mississippi Sound

Abstract

A greater understanding of population dynamics is essential in the management of any species. The Western Gulf stone crab, Menippe adina, is taken as incidental by-catch in the blue crab, Callinectes sapidus, fishery in Mississippi. However, there is a lack of information on the ecology of M. adina in estuaries of the northern Gulf of Mexico. We know that M. adina is associated with hard-bottom habitats such as rock-rubble jetties and oyster reefs and that this habitat is sparse in Mississippi Sound, which mainly consists of soft-bottom habitat. Many studies have demonstrated that habitat complexity is important to several benthic crustaceans because it provides a matrix of different sized refuges that organisms can use to escape from predation. The importance and availability of refugia varies throughout the life history of organisms because of the increase in size of an organism as it grows. Refuge limitation acting on a specific size class may create a demographic bottleneck thereby limiting the production of a population through mortality, migration, or stunting of the affected size class. We tested this refuge limitation bottleneck hypothesis in juvenile stone crabs by supplementing an existing oyster reef with four different sizes of polyvinyl chloride (PVC) pipe. We found that lack of refuge affected both population size structure and density of large juvenile stone crabs on the reef. We also found that competition for available refuges may occur among M. adina and two other xanthid crab species, Eurypanopeus depressus and Panopeus simpsoni. We examined the diet of oyster toadfish, Opsanus beta, in Mississippi Sound and found that the three xanthid crabs comprised a significantly large portion of oyster toadfish diet. Predation by O. beta emphasized the importance of the availability of suitable refugia for the xanthids.