Long-Term Dynamics of U.S. Atlantic Sea Scallop Placopecten magellanicus Populations

Abstract

Biomass and commercial catch rates of Atlantic sea scallops Placopecten magellanicus in the USA generally declined from the 1960s through the mid-1990s as fishing mortality increased. Sporadic large recruitment events temporarily increased landings but also encouraged higher overall fishing effort and thereby contributed to the long-term declines in resource abundance. In 1994, a number of new management measures were introduced, including a moratorium on new permits, limitations on days at sea, gear and crew restrictions, and year-round closed areas. During 1994–2005, the biomass of sea scallops in the U.S. sector of Georges Bank increased by a factor of about 18, while the biomass of sea scallops in the Middle Atlantic Bight increased by about eight times. These increases were primarily due to the area closures. Biomass in the Georges Bank closed areas was 25 times higher in 2005 than in 1994, and the 2005 level constituted over 80% of the biomass in the U.S. portion of Georges Bank. Substantial increases in sea scallop abundance and biomass also occurred in two of the three areas in the Middle Atlantic Bight that were closed rotationally to sea scallop fishing for 3 years. Mean recruitment on Georges Bank did not significantly increase since the closures there, but very strong recruitment has been observed downstream of one of the mid-Atlantic rotational closures. In the open areas, responses to effort reduction measures were minimal until 1999, but biomass, commercial catch rates, and landings substantially increased during 1999–2005 due to effort controls and increased recruitment in the Middle Atlantic Bight. The recovery of U.S. sea scallop populations demonstrates that the combination of effort controls and area management can rapidly rebuild severely depleted fisheries.