Date of Award


Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)


Marine Policy


Teresa R. Johnson

Second Committee Member

Lewis S. Incze

Third Committee Member

Lawrence M. Mayer

Additional Committee Members

Kathleen P. Bell

Keith S. Evans


Soft-shell clams are economically and culturally important to coastal communities throughout Maine, but are experiencing a number of threats including ocean and coastal acidification (OCA). This fishery is regulated through a co-managed system with shared authority between participating coastal municipalities and the Department of Marine Resources (DMR). In 2014, the Maine legislature established a commission to study the influence of OCA on commercially harvested marine species. One recommendation by the commission was to research the effectiveness of calcium carbonate to buffer coastal mudflats, a conservation strategy adopted by some municipal programs to improve clam settlement. The success of this approach is not well quantified and alternative materials should be evaluated in order for managers to make more informed decisions.

Co-management can increase the capacity of managers to respond to changing environmental conditions, such as OCA, and allows resource users to actively participate in the regulatory process. This management structure has built-in flexibility for management to match community priorities and adapt to local concerns, thus leading to variation in management activities. The variation is not well documented for this fishery but provides opportunity to identify underlying patterns in management activities. Our research goals were to (1) assess the variation in the co-management system for Maine’s soft-shell clam resource, and (2) examine the influence on soft-shell clam settlement by calcium carbonate addition to a mudflat.

To quantify management variation, we developed a database from reports submitted in 2014 to the DMR by each municipal program in Maine. We utilized factor analysis to classify underlying patterns and compared the results to community socio-economic characteristics. We also conducted semi-structured interviews with management stakeholders to identify variables not captured in the annual reports. Our results revealed five underlying patterns in management: compliance, investment, meeting frequency, commercial demand, and recreational demand. Few of the community characteristics were significantly related to the factor scores. However, interviews illustrated that involvement of shellfish wardens, support of local government, and the relationship between the municipality and DMR shellfish biologists were important attributes in management programs.

To evaluate agricultural grade limestone as a source of calcium carbonate to influence settlement of soft-shell clams, we conducted an experimental field study in Recompense Bay, Freeport, Maine. Our study occurred in the summer of 2015 and coincided with the known settlement period for wild clams in the area. We compared the number of juvenile soft-shell clams observed in plots treated with limestone to the number of juveniles observed in plots that were untreated. Statistical analysis of our field study indicates that location of clam settlement can be influenced by treatment with limestone but there may be a temporal limitation to its effectiveness.

We drew on the sustainability science and social-ecological systems literature to define the scope of our research and identify attributes to include in our analysis. Using a blended approach that incorporated research questions related to both policy and biology allowed us to understand variation in management activities and contribute information that may be used by managers in decision-making concerning conservation practices.


Joint M.S. in Marine Biology and M.S. in Marine Policy

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