Matrix-based modeling of blue crab population dynamics with applications to the Chesapeake Bay

Blue crab (Callinectes sapidus) plays an important ecological and economic role in estuaries from South America to New England. It supports a large co mmercial fishery in the United States with approximately one third of the l andings taken from Chesapeake Bay. I developed a stage-based matrix model o f the blue crab population to address three key questions: What is the abil ity of blue crab populations to support sustainable exploitation? What stag es of the life cycle are most important in regulating the dynamics of the p opulation? And specific to the Chesapeake Bay, what is the importance of a winter dredge fishery in determining long-term sustainability of the crab p opulation? The model indicated that with the current pattern of exploitatio n blue crab populations are able to sustain a total instantaneous mortality rate (Z) similar to 0.7. If the natural mortality rate is estimated for a maximum life expectancy of 8 yr, this translates to moderate levels of expl oitation (F<0.32). This value is less than the current estimate of exploita tion in Chesapeake Bay (0.9-1.1) indicating that the level of exploitation in this system needs to be reduced to avoid overfishing. Transitions to and from small age-1 crabs were shown to be important in regulating the overal l dynamics of the population. The egg production realized by large adults w as also shown to be an important regulatory process. The model indicated th at reductions in the winter dredge fishery would have a substantial role in ensuring the long-term sustainability of the population. Reductions in oth er sectors of the fishery are also required to ensure sustainability.