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Stage-structured Blue Crab Population Model with Fishing, Predation and Cannibalism
Xu, Fangming
Xu, Fangming
Abstract
Blue crab is a species of crab commonly found in the waters of the western Atlantic Ocean. It is one of the most important shellfish in the Chesapeake Bay. The blue crab fishing industry has a notable impact on the local economy, and blue crabs form a key link in the Chesapeake Bay food web. Between the mid-1990s and 2004, the blue crab population dropped by two thirds. Factors such as habitat loss, harvest pressure and climate change may have contributed to the decline. However, there hasn’t been enough research on the long term dynamic equilibrium, making it difficult to explain the change of the population. In this study, a dynamic population model is built for blue crab using ordinary differential equations. Factors such as reproduction rate, cannibalism, predation rate and fishing mortality are considered, trying to predict the long term stable state under different conditions. Our conclusion is that bistable positive states are not likely to happen with biologically realistic parameter values. Also, crabs can sustain higher fishing pressure under the more realistic assumption of sigmoidal predation/cannibalism than under the constant predation/cannibalism assumption often used in stock assessment models. This model will be useful to evaluate the effects of disease, climate change and overharvesting, and thus help regulators to make appropriate policies and conserve the blue crabs in the Chesapeake Bay.
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2020-05-01
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Mathematics