Management strategy evaluation for the Atlantic surfclam (Spisula solidissima) using a spatially explicit, vessel-based fisheries model

Abstract

Abstract-The commercially valuable Atlantic surfclam (Spisula solidissima) is harvested along the northeastern continental shelf of the United States. Its range has contracted and shifted north, driven by warmer bottom water temperatures. Declining landings per unit of effort (LPUE) in the Mid-Atlantic Bight (MAB) is one result. Declining stock abundance and LPUE suggest that overfishing may be occurring off New Jersey. A management strategy evaluation (MSE) for the Atlantic surfclam is implemented to evaluate rotating closures to enhance Atlantic surfclam productivity and increase fishery viability in the MAB. Active agents of the MSE model are individual fishing vessels with performance and quota constraints influenced by captains' behavior over a spatially varying population. Management alternatives include 2 rules regarding closure locations and 3 rules regarding closure durations. Simulations showed that stock biomass increased, up to 17%, under most alternative strategies in relation to estimated stock biomass under present-day management, and LPUE increased under most alternative strategies, by up to 21%. When incidental mortality caused by the fishery increased, the benefits seen under the alternative management were enhanced. These outcomes suggest that area management involving rotating closures could be valuable in insulating the stock and the commercial fishery from further declines as a northerly shift in range proceeds.The Atlantic surfclam (Spisula solidissima) is an economically valuable bivalve common to the sandy bottoms off the northeastern coast of the United States and Canada (Weinberg, 2005). The range of the Atlantic surfclam before recent effects of global warming spanned the western North Atlantic Ocean continental shelf from Nova Scotia to northern South Carolina, at depths of 10 m to 50 m, and temperature determines the range boundaries (Goldberg and Walker, 1990;Weinberg, 1998 ally not found where average bottom temperatures exceed 25°C (Cargnelli et al., 1999). Atlantic surfclams are relatively sessile planktivorous filter feeders that rarely vacate their burrow unless resuspended by storms or they are escaping predators (Ropes and Merrill, 1973; Prior et al., 1979), after which they rapidly reburrow into the substrate (Weinberg, 2005). The life span of Atlantic surfclam is approximately 30 years and has a maximum-recorded shell length (SL) of 226 mm (Fay et al. 3 ;Cargnelli et al., 1999;Munroe et al., 2016). The range of Atlantic surfclam has been shifting north and offshore since approximately 1970, driven primarily by warming bottom water temperatures (Cargnelli et al., 1999; 3 Fay, C. W., R. J. Neves, and G. B. Pardue. 1983 and Ropes, 1977; Powell 4 ; Hofmann et al., in press) and the shift of the southern fishery from the Delmarva Peninsula to ports north . From the 1997 to 1999 period, the Atlantic surfclam population was considered to be near carrying capacity (NEFSC 2 ). Abundances were once high on the continental shelf off the Delmarva Peninsula, but declines in grow...

Potential Repercussions of Offshore Wind Energy Development in the Northeast United States for the Atlantic Surfclam Survey and Population Assessment

“…Details of the SEFES model framework are provided by Munroe et al (2022), andScheld et al (2022) provide details of the economic analyses used to assess the fishing fleet and processor operations. Previous implementations of SEFES were used to evaluate temperature-induced range shifts in Atlantic surfclam distribution and associated effects on the stock, fishery, and management (Powell et al 2015Kuykendall et al 2017Kuykendall et al , 2019Stromp et al 2023, this themed issue). Assessment of the skill of simulations implemented with SEFES using a variety of fisheryindependent and fishery-dependent data showed that the model provides a reasonable representation of the existing fishery (e.g., Munroe et al 2022).…”

An Overview of Factors Affecting Distribution of the Atlantic Surfclam (Spisula solidissima), a Continental Shelf Biomass Dominant, During a Period of Climate Change

“…The surfclam MSE allows evaluation of alternative management strategies that simultaneously address the two primary challenges facing sustainability of the surfclam stock and fishery: range contraction limiting stock abundance and a decline in the number and density of dense surfclam patches limiting the fishery. Simulations that implemented rotating closures as a management tool, based on the success of this approach for sea scallops Placopecten magellanicus (Hart & Rago 2015), were used to evaluate the effects of closure durations from 3 to 7 years, criteria for identifying areas for closure based on the true abundance or the proportional abundance of small surfclams, and a range of definitions for a small surfclam based on the time required for growth to market size (120 mm) (Kuykendall et al 2017).…”

“…In addition, closure of one 10-min square per year resulted in increased LPUE because the areas opened each year contained highdensity surfclam patches. Thus, area management based on time-limited closures enhanced the stock and improved the fishery (Kuykendall et al 2017).…”

“…The MSE identified rotating closures as a management option that may provide improved stock performance and improved fishery economics (Kuykendall et al 2017). This approach takes advantage of the rapid growth of surfclams to market size and patchy recruitment, and the landings are measured in volume rather than number.…”

“…This northeastward and offshore progression has been attributed to warming of MAB bottom waters (Weinberg et al 2002, Weinberg 2005. The decrease in biomass and shift in range has had significant implications for the surfclam fishery and its management (McCay et al 2011, Powell et al 2015a, Kuykendall et al 2017.…”