A Model for Assessment of Impacts of Brown Shrimp Fishery Management Closures in the Gulf of Mexico

An age-structured model fo the Gulf of Mexico brown shrimp fishery was developed to study the impacts of seasonal management closures on biological and economic yields. The basic premise of the model is to prohibit fishing on juvenile shrimp, allowing the population to increase to a larger, more valuable size. The model consists of three regional submodels, each having inshore, nearshore and offshore populations. A virtual population analysis (VPA) of fishery-dependent statistics was employed to obtain input data for initial stock sizes, recruitment levels, and fishing mortality rates. Shrimp emigration from inshore waters to deeper depths was determined by tracking the catch of size-specific cohorts. Simulated harvests are validated with actual landings and benefits to vessel owners can be calculated. Results indicate large increases in landings, revenues and profits with simultaneous gulfwide closures of offshore waters. Impacts of the inshore fishery on offshore production is also estimated with this model.