Date of Award

Spring 5-14-2016

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Policy

Advisor

Teresa R. Johnson

Second Committee Member

Paul D. Rawson

Third Committee Member

Sara M. Lindsay

Additional Committee Members

Samuel P. Hanes

Abstract

Commercial fishermen in Maine are increasingly dependent upon the American lobster fishery, and this reliance on a single species poses a threat to working waterfronts. Aquaculture represents a potential opportunity for commercial fishermen to diversify their income. Literature on the adoption of innovation suggests that factors such as age, education level, fishing experience, diversification, and leadership are important predictors of early adoption of innovation. However, few studies have examined whether such factors affect the adoption of aquaculture by commercial fishermen. Our marine policy research studied fishermen enrolled in two pilot shellfish and seaweed aquaculture classes held in 2013 in Harpswell and Corea, Maine. Those enrolled in the classes can be considered early adopters of innovation. To better understand these early adopters and their perceptions of aquaculture as a means of income, we conducted a total of 33 semi-structured interviews before and after the course with fishermen who did and did not finish the course. Those who had broader experience and more years of experience, as well as those having demonstrated some form of leadership in fisheries cooperatives, were more likely to adopt. Potential barriers to the adoption of aquaculture were mostly related to risks associated with an uncertain return on investment. The results from this study will inform the structure of future aquaculture training courses as well as highlighting additional avenues of research on the adoption of aquaculture by commercial fishermen.

Those starting aquaculture farms face many challenges, among them parasites such as the blister worm, Polydora websteri. This polychaete burrows into shells of several commercially important shellfish species, including the eastern oyster. As the oyster industry has grown, so has the impact of this worm. Oysters served on the half shell are not only less attractive when infested by worms, but mud and detritus can leak out during shucking and create off-flavors. Farmers are concerned about their reputation if blister worm-infested oysters are sent to market. Various kinds of chemical, fresh water, and brine baths have been used to treat blister worm infestations, but none has reliably eliminated worms in established burrows. The Bagaduce River Oyster Company (BROC) has developed the only known effective method of killing the worms without causing damage to the oysters. They place their oysters in cold storage for three weeks or more during the winter months – a method which is generally not harmful to the oyster but kills the adult blister worm. This treatment, however, is labor intensive and can result in lost production time. Our marine biology research explored whether periodic air-drying and pressure washing could reduce the settlement of larval P. websteri and block blister worm infestations before they occur. Oysters were air-dried for 4 h or 24 h, or air-dried and washed, every other week. Ten to twenty oysters were sampled from each treatment bimonthly from May through October 2014 and examined for the presence of newly constructed worm burrows. Additionally, plankton tows were taken on each side of the oyster farm to track the abundance of blister worm larvae in the plankton. Air-drying alone resulted in a substantial decrease in the formation of new blister worm burrows in experimental oysters. Although washing resulted in additional decreases in the number of new burrows, the impact of washing was not statistically significant. Our results suggest that regular air-drying and washing of oysters can reduce the impact of P. websteri at oyster farms in Maine that employ surface culture and reduces the need for complex treatments to rid oysters of blister worm infestations.

Comments

This thesis is submitted in partial fulfillment of the requirements for the degrees of Master of Science in Marine Biology and Master of Science in Marine Policy (in the dual degree program of the School of Marine Sciences at the University of Maine).

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