FORECASTING THE FISHERY FOR PINK SHRIMP, PENAEUS DUORARUM, ON THE TORTUGAS GROUNDS, FLORIDA

摘要

In this report I review the biology of and fishery for pink shrimp, Penaeus duorarum, harvested from the Tortugas Grounds off southwest Florida, and present models used to forecast annual pink shrimp landings in this area. Pink shrimp spawn all year, and larvae recruit to nurseries in the seagrass-mangrove ecosystem surrounding Everglades National Park and Florida Bay. Juveniles move out of the nurseries all year, but catch per unit of effort for smallest size classes generally exhibits March and September peaks. Total landings usually rise sharply in November and taper off after April. The fishery was relatively stable during 1960-85, averaging 4,350 metric tons annually, but it has shown a singular decline and potential recovery since 1985. In 1987, I began forecasting annual landings by using multiple regression analyses of fishery catch statistics and environmental factors that could affect survival, growth, and recruitment. Potential predictor variables from May through October were investigated in order to release a timely annual forecast by November. Each year, the updated data set from 1966 onwards was examined to derive the ''best'' forecast models. Important predictor variables included indices of fishing activity during the waning months of the fishery (May-July) and surface and ground water levels within Everglades National Park during June-September. Forecasts were within +/-20% of actual landings for five of eight years, whereas forecast direction (increase or decrease over the prior year) was usually correct. Cause-effect relationships between predictor variables and pink shrimp recruitment to the fishery remain to be determined.