Date of Award

5-2006

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Yong Chen

Second Committee Member

James Wilson

Third Committee Member

Linda Mercer

Abstract

In the nearshore Gulf of Maine, Jonah crab, Cancer borealis, has been an incidental catch of the lobster industry for nearly a century. Recent increases in the landings and apparent abundance of Jonah crab initiated new interest in a potential fishery. Little information is known about the life history of the Jonah crab and neither state nor federal management directly regulate the Jonah crab. My research, driven by fishermen interest and the Maine DMR’s concern about insufficient knowledge for the barely regulated Jonah crab, begins to delve into the basics of developing an effective fisheries independent crab survey, the present characteristics of fishing mortality, and the crab fishery potential. I assisted in the development of a video survey targeting crab in Spring 2004 and evaluated the effectiveness of the approach. Despite the small sample size, I conclude that in the early spring, crabs likely associate with complex habitat and shallow water and are strongly influenced by temperature. I estimate key life history parameters using a length frequency analysis method, develop biological reference points, and then compare them with current fishing mortality estimates to determine the population status. I conclude that the present fishing level is unlikely to be overfishing the stock, but there is a high level of uncertainty associated with the assessment. The experimental Jonah crab trap project explores the potential of a directed Jonah crab trap and fishery. In the duration of the project, interest and participation by fishermen greatly diminished along with the landings of crab coast wide, but my observer trips and analysis of the participant logbook reports provide evidence that the experimental trap reduces bycatch of regulated species and could be used for commercial harvest of crabs. A socio-economic survey sent to active and non-active participants to determine fishermen’s motivations found most fishermen acquired a permit to take advantage of a new opportunity to diversify their catch if crab became a directed, but limited, fishery. The fishermen saw the potential of a new fishery if the market value improved. The future use of the Jonah crab specific trap has a number of obstacles including the continued effort and potential of the full lobster industry and the protected resource issues of minimizing whale entanglements with fixed gear by reducing that gear in high risk areas. My research takes the first crucial steps to approach Jonah crab from the biological, social, and fisheries perspective needed to begin to evaluate prospective management, but the scope of knowledge in Jonah crab biology and its role in the Gulf of Maine ecosystem needs to be increased. I found the lack of a market and limited access to crab has prevented reckless and unsustainable harvest of Jonah crab in the nearshore Gulf of Maine, but under other conditions, the effort could increase. Managers from all the states that report Jonah crab landings must work together to better characterize the scale of effort inshore and offshore on the stock and determine the risks and potential increase of effort on the Jonah crab.

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