Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Interdisciplinary Program

Advisor

James Wilson

Second Committee Member

Joshua Stoll

Third Committee Member

Keith Evans

Additional Committee Members

Christine Beitl

Michelle Staudinger

Abstract

Atlantic Cod Gadus morhua has been subject to commercial exploitation since the thirteenth century. An analysis of cod fisheries over space and time reveals a pattern of serial depletion that reflects the cross-scale interaction of fish population structure, economic incentives, developments in fishing technology, and government efforts to limit access to fishing areas. The meta-population structure of cod populations allows overharvesting, even when strict but broadscale controls are in place. Three case studies illustrate a pattern of fish population depletion followed by expansion of fishing activity that repeats at a range of scales. Sustainable use of a commons, rare among fisheries, is attributed to conditions that constrain users to a defined territory, limit the number of users, and align such a territory with local conditions. Constrained by boundaries, fishermen’s incentives shift from maximizing harvests in the short term to ensuring sustained harvests over the long term. Fishermen learn from others where to fish when they find it less costly to do so than than to search for fish themselves. When a fishing territory is congruent with local components of a metapopulation, sharing information, a form of social learning, allows fishermen to develop a refined, collective understanding of subpopulation dynamics and can lead to group formation and the capacity to address unsustainable harvests and other collective action dilemmas. Co-management, the sharing of responsibility for management between fisheries agencies and fishermen, allows for local information to be incorporated into the management process and for fishermen to test management strategies based on their understanding of population dynamics. It reduces the costs for fisheries agencies of monitoring and understanding fine scale conditions and allows for local action that they cannot manage. Analysis of comanaged fisheries in Maine, for lobster, clams, river herring, and scallops, indicates that comanagement improves fisheries productivity and is more effective than standard, top-down, broad-scale fisheries management.

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