Date of Award

Spring 5-8-2020

Level of Access Assigned by Author

Open-Access Thesis

Language

English

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Yong Chen

Second Committee Member

Keith Evans

Third Committee Member

Joshua Stoll

Additional Committee Members

Anne Richards

Abstract

Northern Shrimp (Pandalus borealis) once supported a key commercial fishery in the State of Maine. Since its closure in 2013, the stock has remained in a particularly vulnerable state following recruitment failure, overfishing, and rising water temperatures. Furthermore, without this source of supplemental income, local fishermen have also experienced financial stress following unstable fishing conditions in other fisheries. The collective goal of this research project was to assess factors impacting the feasibility of reopening and maintaining this vulnerable winter fishery. These goals are addressed over 4 chapters. Chapter two offers insight regarding what is most often omitted from the regulatory process in fisheries management, including fisher acumen and cooperative opportunities to broaden the coalition for stewardship among resource users. By examining qualitative data collected through survey efforts, fishermen provide a first-hand account of fundamental and broadly applicable circumstances that impact fisher behavior, often resulting in inefficient outcomes in fisheries management. Collectively, qualitative data collected through industry based surveys highlight relevant environmental, biological, socioeconomic, and fishery-specific factors hindering the development and implementation of more efficient management practices. Assessment of the response of shrimp to changing environmental conditions and anthropogenic activity is critical to accurately determine appropriate fishing levels, especially given the lowered ability of the stock to build resilience. In Chapter three, I explore the relationship between size-at-transition and potential environmental and anthropogenic sources of influence impacting this biological process. Results showed that size-at-transition is more strongly influenced by environmental conditions experienced by northern shrimp as juveniles. Specifically, surface temperatures observed throughout the summer and fall seasons inshore were most significant, with decreases in size-at-transition observed at higher temperatures. Size at which shrimp transition from male to female is a critical stage in the life history strategy of northern shrimp. Given the vulnerable state of the fishery, managers will need to account more strongly for decreases in reproductive potential associated with smaller female body size. Such information is important to incorporate into future regulatory strategies in support of the stock’s restoration. It is hypothesized that decreases in size-at-transition will continue to occur considering rising water temperatures; additional studies show that warm water accelerates metabolic growth rates in juvenile shrimp, facilitating increased molting frequency with lower overall growth observed. Consistent with past trends, it is likely that shifting environmental conditions will continue to have adverse impacts on the northern shrimp fishery in the Gulf of Maine (GOM). If the fishery is to reopen, managers will likely be forced to make tough decisions regarding effort and participation if they intend to establish an ecologically and economically sustainable fishery. In the fourth and final chapter, I utilize a fishery-level production function to understand what suite of factors most strongly influence output (i.e. landings) within the fishery, highlighting key differences in strategy between both trap and trawl gear types. Furthermore, results of this analysis provide insight into the relationship between effort and shifts in harvestable biomass. A deeper understanding of sources of vulnerability and factors impacting a fisherman’s adaptive capacity is crucial for the development of more effective management strategies. Used as a proxy for shifting environmental conditions, monthly remaining biomass exhibited a positive relationship with northern shrimp landings for both gear types, as did landings and certain input effort factors such as sea time, number of traps used (trappers), and number of tows (trawlers). Results suggest that certain gear types are likely to experience increased vulnerability than others, and increased control on effort will likely be necessary to better control landings within the fishery. Shortcomings within each chapter are observed, namely due to inconsistent data collection efforts and a shortened times series regarding the data utilized within each study. Despite relatively short time series of data included, this study provides important information to help determine fleet size and effort levels should the fishery reopen in the future. Collectively, the information obtained through these studies provide valuable insight regarding 1) the impact shifting environmental conditions may continue to have on the fishery, and 2) ways in which fishers and managers may account for these shifts while facilitating cooperative efforts in the interest of biological and socioeconomic stability within the fishery.

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