Evaluation of effort reduction in the Florida Keys spiny lobster, Panulirus argus, fishery using an age-structured population analysis

Abstract

A management programme implemented in Florida in 1993 was designed to reduce the number of traps in the spiny lobster fishery in order to reduce gear conflicts, environmental damage and effort without reducing harvest. Traps in the commercial fishery were reduced from 939 000 in 1991 to 568 000 in 1995. Landings by fishing season, zone (upper Florida Keys and lower Florida Keys), sex, and time period (summer v. winter) were pro-rated into numbers by length that were assigned ages by using growth simulations. From tag–recapture data, moult interval was estimated by using a logistic regression with terms for zone, sex, time period, carapace length, and time at large. For lobsters that moulted, the moult increment was modelled with a multiple regression including the same terms. Standardized catch-per-trip and total landings increased as traps were reduced. Age-structured analysis of the catches-at-age indicated that fishing mortality decreased by 16%, even as landings increased. It is not known whether the increase in landings was due to natural population fluctuations or to positive results of trap reduction. Fishing mortality rates still exceed common benchmarks used in fishery management, and excessive traps remain in the fishery.