Large-scale closed areas as a fishery-management tool in temperate marine systems: The Georges Bank experience

Seasonal closed areas have been an element of fishery management in New Eng land waters since 1970 but before 1994 had limited impact on the conservati on of groundfish stocks for which they were de:signed. Beginning in Decembe r of 1994, three large areas of historic importance to groundfish spawning and juvenile production on Georges Bank and in Southern New England, totali ng 17,000 km(2), were closed year-round to any gears capable of retaining g roundfish (trawls, scallop dredges, gill nets, hook fishing). In the ensuin g five years, the closed areas contributed significantly to reduced fishing mortality of depicted groundfish stocks. Placements of the closed areas af forded the greatest year-round protection to the shallow-sedentary assembla ge of fishes (primarily flounders, skates, and miscellaneous others) and bi valve molluscs, Although the closures afforded less year-round protection t o migratory age groups of Atlantic cod, Gadus morhua, and haddock, Melanogr ammus aeglefinus, additional new regulations in open areas and in the Canad ian portions of Georges Bank also contributed to the observed reductions in stock-wide fishing mortality rates. The areas were closed to dredge gear d esigned for sea scallops, Placopecten magellanicus, because of groundfish b y-catch (particularly of flounders). Scallop biomass increased 14-fold with in the closed areas during 1994-1998. In July 1998, total and harvestable s callop biomasses were 9 and 14 times denser, respectively, in closed than i n adjacent open areas. A portion of the closed areas was designated a "habi tat area of particular concern" on the basis of patterns of occurrence of j uvenile groundfish in gravel/cobble sediment types. Managers reopened porti ons of one closed area to sea-scallop dredging in 1999, but restrictions on gear and areas fished were used to minimize groundfish by-catch and impact on juvenile cod and haddock on gravel substrates. Results from these reope nings have encouraged managers to contemplate a formal 'area rotation' sche me for scallops intended to improve yield per recruit. Closures of large po rtions of Georges Bank have proved to be an important element leading to mo re effective conservation of numerous resource and nonresource species, des pite selection of the closed areas on the basis of seasonal spawning ground s of haddock and the distribution of yellowtail flounder, Limanda ferrugine us, in southern New England. In the future, factors other than fishing mort ality reduction, including optimal placement to enhance larval production a nd to protect nursery areas and spawning concentrations, may well influence the selection of closed-area boundaries.