DThe Value of Captains’ Behavioral Choices in the Success of the Surfclam (Spisula solidissima) Fishery on the U.S. Mid-Atlantic Coast: a Model Evaluation.

Abstract

The response of the surfclam Spisula solidissima to warming of the Mid-Atlantic Bight is manifested by recession of the southern and inshore boundary of the clam's range. This phenomenon has impacted the fishery through the closure of southern ports and the movement of processing capacity north, impacts that may require responsive actions on the part of fishery captains to mitigate a decline in fishery performance otherwise ineluctably accompanying this shift in range. The purpose of this study was to evaluate options in the behavioral repertoire of captains that might provide mitigation. A model capable of simulating a spatially and temporally variable resource harvested by fleets of boats landing in a number of homeports was created. The model includes characterization of each vessel in terms of economics and vessel performance. The model assigns to each vessel a captain with defined behavioral proclivities including the tendency to search, to communicate with other captains, to take advantage of survey data, and to integrate variable lengths of past history performance into the determination of the location of fishing trips. Each captain and vessel operate independently in the simulation providing a spatially and temporally dynamic variability in fishery performance. Simulations showed that a number of behaviors modestly varied performance. Use of survey data and occasional searching tended to increase performance. Reliance on an older catch history tended to reduce performance as did frequent searching. However, in no simulation was this differential large and the differential was little modified by the contraction in the surfclam's range. Simulations showed that the population dynamics of the clam and the low fishing mortality rate imposed by the Fishery Management Plan permit near optimal fishing performance based on a few simple rules: choose locations to fish that minimize time at sea while permitting the landing of a full vessel load; base this choice on the most recent catch history for the vessel. Simulations suggest that the performance of the fishery is primarily determined by surfclam abundance and the location of patches that control LPUE at small geographic scales. Constraints imposed on fishery performance by port location and vessel size far exceed limitations or ameliorations afforded by modifications in the behavior of captains.

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

“…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.…”

“…The surfclam population is composed of source and sink subpopulations that are directly impacted by changing environmental conditions, the effects of which determine trends in overall population biomass, mortality, abundance, and reproduction. The environmental, ecological, and biological interactions produce biomass distributions that interface with the surfclam fishery and management structure through the statutorily mandated quota-setting process and through private business decisions and voluntary collective behavior (see overviews in McCay et al 2011, Powell et al 2015a.…”

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

“…Powell et al (2015) provides a complete description of the capabilities of this model. MA) and analyzed with SAS statistical software, vers.…”

“…All captains in this study had a skill level of 10. See Powell et al (2015) for a more detailed description of "captain memory development" and skill levels. Each simulation spans a total of 201 years.…”

“…The SEFES model permits simulation of the entire fishing fleet and each vessel operating independently according to specified criteria. Powell et al (2015) provide a detailed model description. Pertinent details for this study are summarized here.…”