Joseph E. Powers

A Commentary on Western Atlantic Bluefin Tuna Assessments

Abstract Intense fishing for bluefin tuna Thunnus thynnus in the western Atlantic Ocean began in the 1960s, when landings peaked at nearly 20,000 metric tons (mt). During the 1970s, landings averaged about 5,000 mt. The International Commission for the Conservation of Atlantic Tunas (ICCAT) established a total allowable catch (TAC) of 1,160 mt in 1982 and has set limits ranging from 1,995 to 2,660 mt annually since. The Commissions assessments indicate that unrestricted fishing through the 1960s and 1970s resulted in a sharp decline in abundance, primarily because heavy fishing on young fish wasted potentially good recruitment. Since the late 1980s, ICCAT management has stabilized the western Atlantic population, and recently there are signs of improvement. Resource assessments and management of western Atlantic bluefin tuna are subjects of severe controversy. Two of the most controversial issues are the stock assessment implications of fish migrations between the western and eastern Atlantic management ...

Maximum Sustainable Yield and Bycatch Minimization “to the Extent Practicable”

Abstract Two goals of marine fisheries management in the USA are (1) to achieve maximum sustainable yield (MSY) and (2) to minimize bycatch “to the extent practicable.” However, the determination of MSY is contingent on the selectivity of the various fisheries involved and the mix of these fisheries that managers desire. I compare several methods of computing MSY and associated parameters that involve alternative assumptions about the balance between target and bycatch fisheries. These methods were evaluated using a deterministic population simulation model. Additionally, biological risk was evaluated by computing relative spawning levels in the presence and absence of bycatch. While the choice of the method will largely be driven by socioeconomic factors, some implications for management are discussed. Before analysts can calculate MSY and associated parameters, managers must determine their desired mix of fishing and the definition of “to the extent practicable.”

Strategic Interaction in United States Fishery Management Councils

A two-stage model of interactions within Regional Fishery Management Councils was developed in which management targets were set which may deviate from levels needed to achieve management policy. The first stage modeled bargaining solutions between Council members (harvesters, conservationists, and government) for management targets, and the second stage addressed litigation of those solutions. Results indicate that bargaining power favoring one constituent group could lead to Council outcomes that deviate from management policy. This, in turn, creates incentives for the aggrieved constituent group to litigate. Tradeoffs between benefits and costs of litigation and governmental strategies to address these issues are explored.

A Comparison of Red Snapper Reproductive Potential in the Northwestern Gulf of Mexico: Natural versus Artificial Habitats

AbstractThe majority of the research on adult Red Snapper Lutjanus campechanus in the Gulf of Mexico has been conducted at artificial habitats (in particular, low-relief artificial reefs off the coast of Alabama) and more recently on oil and gas platforms off the coast of Louisiana. However, previous studies indicate that there are differences in Red Snapper demographics and reproductive biology between habitats and regions within the Gulf. Despite the lack of study of natural reefs and banks in the Gulf, these areas are believed to be the historical centers of Red Snapper abundance. This study sampled Red Snapper from habitats that include reefs located more than 125 km offshore, making them difficult to reach for routine sampling. The results indicate significant differences in Red Snapper reproductive biology between females collected on adjacent artificial and natural habitats. Annual fecundity estimates were almost 20-fold higher in fish collected from natural habitats. Due to the high number of arti...