Jointly Modeling Fish and Fishing in the Maine Lobster Fishery

Models of fisheries often assume very simplistic functional relationships between fishery biomass, fishing effort, and catch often assuming catches and revenues simply change linearly in proportion to effort and biomass. In reality the relationships between biomass, effort and catch can be sensitive to the spatial distribution of the resource and the interdependent behavior of fish and fishermen. Catchability as well as fish value can vary substantially over time, both within and between years. In the case of the Maine lobster fishery the catch per unit effort varies greatly over the year and the value of the catch is impacted by when it is landed. The fishery is subject to seasonal depletion, congestion effects and prices that are strongly affected by monthly landings. The relationship between catchability and biomass also appears to have changed substantially over time as the fishery and the resource have grown. I use a bioeconomic model of the fishery that incorporates empirically estimated vessel-level production functions to evaluate the optimal level and seasonal distribution of catch and effort. I also evaluate how that might change if recruitment to the fishery, which appears to be heavily influenced by environmental factors, returns to the levels prevalent prior to the expansion of the fishery in the 1990s.