Date of Award

12-2005

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Oceanography

Advisor

Leslie Watling

Second Committee Member

Peter Auster

Third Committee Member

Lawrence Mayer

Abstract

Otter trawling, a common method to catch commercially valuable groundfish, has been shown to reduce benthic habitat complexity by the direct reduction of abundance levels of epifaunal and infaunal species. Such reductions in benthic biodiversity may have long-term consequences for ecosystem resilience and function of benthic habitats. In the Gulf of Maine, in order to address concerns of declining groundfish stocks while simultaneously conserving benthic habitats, marine protected areas (MPA) have been designated that restrict groundfish trawling. One such MPA, the Western Gulf of Maine Closure (WGOMC), encompasses regions that, as of 2004, had been closed to trawling for 6 and 4 years, respectively. Such a time frame allows the question, how have benthic communities responded to the cessation of chronic groundfish trawling? To address this question, an observational study was conducted where the community composition of coarse sediments in the WGOMC at different times were compared to coarse sediment community composition of an actively trawled fishing ground (the Kettle) at a similar depth. Video transects of epifaunal communities were taken in the WGOMC in August 2002 (2-year closed sites). Video transects of the epifaunal community and grab samples of the infaunal community were taken in the Kettle in August of 2003 (Open 2003), and resampled in August 2004 (Open 2004). Finally, video transects and grab samples were taken again in the WGOMC in August 2004 in what were the 2-year closed sites (now the 4-year closed sites), and in the 6-year closed region of the WGOMC (6-year closed sites). Multivariate analysis showed significant differences in benthic community composition between the Kettle and the WGOMC which could be attributed to the cessation of chronic trawling disturbance. In general, benthic communities in the Kettle were dominated by more disturbance tolerant, opportunistic families, while communities in the WGOMC were dominated by more disturbance intolerant, sessile families.

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