Improving Utilization of the Atlantic Sea Scallop Resource: an Analysis of Rotational Management of Fishing Grounds

An age-structured bioeconomic model was constructed to determine optimal patterns of exploitation for the U.S. Atlantic sea scallop fishery. Results indicated that economic rents are maximized by engaging in pulse fishing strategies, whereby fishing only occurs following a multi-year closure period. Closures allow biomass to accumulate undisturbed for several years in a row, leading to the harvest of premium-size scallops upon reopening of the fishing grounds. Closures also result in substantial reductions in operating fishing costs. The rotational harvesting strategy was found to be robust with respect to a number of assumptions in the model. Policy implications are discussed. INTRODUCTION The Atlantic sea scallop, Placopecten magellanicus, is a bivalve mollusk that occurs on the eastern North American continental shelf. Major aggregations are found in the Mid-Atlantic from Virginia to Long Island, on Georges Bank, in the Great South Channel, and in the Gulf of Maine (Figure 1). U.S. meat landings in 2003 exceeded 25,000 metric tons (MT), a historical record, with ex-vessel revenues reaching almost $230 million, making the sea scallop fishery one of the most valuable in the northeastern United States (second only to lobster). Captures from the U.S. fishery have fluctuated considerably over the years. Landings increased substantially after the mid-1940's, with peaks occurring around 1960, 1978, 1990, and in the most recent period (2001-2004). The U.S. portion of Georges Bank witnessed a dramatic decline in productivity during 1993, with landings remaining low until 1998 (Figure 2). Historically, the Mid-Atlantic Bight area has been less productive than Georges Bank; however, there has been an upward trend in both recruitment and landings in the area since the mid-eighties (NEFSC 2004). Scientists agree that unusually strong recruitment in the Mid-Atlantic Bight has been a key contributor to the record landings achieved in the most recent years. Sea scallop fisheries in the U.S. Exclusive Economic Zone (EEZ) are managed under the Atlantic Sea Scallop Fishery Management Plan (FMP), initially implemented in May 1982. During the initial years regulation was primarily based on a minimum average meat weight requirement for landings. The nearcollapse of the fishery in Georges Bank during the mid-1990s prompted drastic changes in management philosophy. The Amendment #4 to the FMP (NEFMC 1993), implemented in 1994, shifted management away from meat count regulations to effort control measures, including incrementally increasing restrictions on days-at-sea (DAS), minimum ring size, and crew limits. In addition, approximately onehalf of the productive scallop grounds on Georges Bank were closed in December 1994. In the MidAtlantic, two areas were closed for three years starting in 1998 to protect aggregations of small scallops (Figure 1). Area closures had an immediate effect on scallop abundance and biomass; for example, it is estimated that over 80% of the sea scallop biomass in the U.S. portion of Georges Bank is currently in areas closed to fishing (NEFSC 2004). Portions of Georges Bank closed areas were temporarily opened for 1 Cite as: Valderrama, Diego and James L. Anderson. 2006. Improving utilization of the Atlantic sea scallop resource: an analysis of rotational management of fishing grounds, p. 179-195. In: Sumaila, U. Rashid and Marsden, A. Dale (eds.) 2005 North American Association of Fisheries Economists Forum Proceedings. Fisheries Centre Research Reports 14(1). Fisheries Centre, the University of British Columbia, Vancouver, Canada. 2 Email: [email protected] Rotational management of Atlantic sea scallops, D. Valderrama and J.L. Anderson 180 limited scallop fishing during 1999-2001, resulting in the capture of exceptional amounts of very large scallops. Remarkable landings have also been achieved from controlled-access programs to the closed areas in the Mid-Atlantic Bight since 2001. Figure 1. Major regions for Atlantic sea scallop fishing in the U.S. The most important aggregations are found in Georges Bank and the Mid-Atlantic Bight. The Mid-Atlantic closed areas have been managed under special access programs since 2001. The success of the temporary access programs led to the formulation of a new set of regulations, Amendment #10, implemented in 2004 (NEFMC 2004a). This amendment proposes a spatially-based management system, with provisions and criteria for new rotational closures, and separate days-at-sea allocations for reopened closed areas and general open areas. Under this amendment, restricted access to portions of two of the Georges Bank closed areas during the fall of 2004 was approved. Preliminary reports indicate that the reopened areas have again yielded large amounts of "frisbee-sized" scallops (McGovern 2004). Amendment #10 also introduced new gear regulations to improve selectivity towards larger scallops and to reduce the amount of associated bycatch. Sea scallops and rotational management There is already considerable evidence that rebuilding of sea scallop biomass in heavily overfished areas can be conducted much more efficiently through area closures than with effort control regulations such as meat count requirements or limited crew sizes. For example, biological surveys conducted in 1998 indicated that total and harvestable scallop biomasses were 9 and 14 times denser, respectively, in closed than in adjacent open areas in Georges Bank (Murawski et al. 2000). Evidence clearly suggests that the sea scallop fishery would benefit greatly from a formal "area rotation" scheme of fishing grounds. This same approach has been proposed or is being used for other sedentary species such as sea urchins, sea cucumbers, corals, and abalone (Lai and Bradbury 1998; Heizer 1993; Caddy 1993; Botsford et al. 1993; Sluczanowski 1984). Sea scallops appear to be ideal candidates for rotational fishing because 1) they have low mobility, moving at most a few miles per year; 2) they grow quickly and are relatively long-lived; and 3) they exhibit low natural mortality (around 10% per year). Gulf of Maine groundfish closed areas Mid-Atlantic closed areas (1998-2001) Chesapeake Bay USA Canada Georges Bank groundfish closed areas (1994 – Present) 2005 NAAFE Forum Proceedings, U.R. Sumaila and A.D. Marsden 181 0 4 8 12 16 20 24 28 198