EFFECTIVENESS OF SIZE LIMITS AND BAG LIMITS FOR MANAGING RECREATIONAL FISHERIES: A CASE STUDY OF THE GULF OF MEXICO RECREATIONAL GAG FISHERY

Restrictions on the number and size of fish that can be retained are among the most common recreational fishing regulations used to maximize sustainable harvest levels and protect fish stocks from overfishing. The effectiveness of these regulations is contingent on the assumption that most fish that are released due to regulations survive. We developed an equilibrium population model to examine the trade-offs among sustainability, harvest, and regulation efficiency across a range of minimum size limits, bag limits, discard mortality rates, and fishing mortality rates. We used the model to evaluate the utility of size and harvest limits for the Gulf of Mexico recreational gag, Mycteroperca microlepis (Goode and Bean, 1879), fishery. We show that when discard mortality is present, the ability of size and bag limits to decrease exploitation is diminished as released fish are removed from the population as dead discards. Given current levels of fishing mortality rates in the gag fishery, restrictive size and bag limits are necessary to prevent recruitment overfishing. However, because of high discard mortality rates (approximately 20%), these regulations result in reduced attainable yields and high waste due to dead discards (low efficiency). In addition, the current levels of fishing mortality and discard mortality place the recreational gag fishery at the edge of sustainability such that an increase in either discard mortality or fishing mortality could cause recruitment overfishing.