Dynamical Modeling of Complex Fish-Fisheries Interactions

Dynamics in fishery ecosystems are forced by natural interactions between species, oceanographic processes, and human activity through fishing.  We use a dynamical modeling approach to explore linkages between American lobster, Atlantic herring, and Atlantic cod populations in the Gulf of Maine. An initial model of the natural system demonstrates simple predator-prey interactions among the three populations (cod prey on lobsters and herring, herring prey on larval cod).  A second model incorporates the impact of fishing on the three species under various fishing mortalities and fleet dynamics.  This model also includes an important connection between lobster and herring: herring are used as bait in the lobster fishery and herring bait is now an important food source for lobsters.  We compare the fish populations under a dynamic fleet of fishermen who are able to switch between fisheries and a static fleet that has to stick to one species.  This is important for fishery managers attempting to move toward an ecosystem-based approach.