Co-management is considered an alternative approach to fisheries management, however, not all co-managed fisheries have been successful. Most studies discussing the success and failure of co-management have emphasized economic and social attributes of success and failure, such as fishery rights and institutional arrangements. The effect on co-management of biological characteristics, such as the growth rate of the fish stock and the stock size, has gained little attention. This study investigates the influence of intrinsic growth rate (r) and relative stock size (B') on fishers' decision to cooperate with catch quotas. The concept of mixed strategies from game theory is incorporated with basic economic concepts and a biomass dynamics model to capture important aspects in a fishery cooperative. The discounting concept is applied to capture the fishers' tendency to cooperate (��[subscript i]). Profits from fishing are specified for each fisher within a 2 by 2 matrix with two players and two strategies (cooperative and non-cooperative). When both players have dominant strategies, where one player's best strategy coincides with the other player's best strategy, the game has a pure strategy equilibrium. Alternatively, the equilibrium outcome of the game is determined using mixed strategies. The results indicate that the biological parameters, r and B', influence fishers' cooperation. However, social parameters (��[subscript i]) and economic parameters (profit/cost ratio when the stock is at the carrying capacity) must also be considered. Furthermore, this study finds that the fishers are more likely to play the cooperative strategy over very wide ranges of r and B' when their tendencies to cooperate are high. In contrast, the fishers are more likely to play mixed strategy when their tendencies to cooperate are low. Having a large discrepancy between the fishers' tendencies to cooperate has less influence on the outcomes of the game than having high values for the fishers' tendencies to cooperate. The profit/cost ratio generally accentuates the most frequent outcomes of the game. For instance, if the outcomes are mostly mixed strategies, a higher ratio expands the mixed strategy outcomes over wider ranges of r and B'. / Graduation date: 2001

The depletion of a great many conventional fish stocks is urgent testimony for fisheries management to evaluate risk and uncertainty in an interpretable manner. We propose a novel decision based approach to time-series analysis that explores the spectrum of alternative population trajectories, each of which can be formulated as hypotheses about the state of the fishery. In the first chapter, we evaluate the ability of different regions of the surplus production state space to describe the true state of three North American fisheries: Pacific cod, porbeagle shark and yellowtail flounder. We consider how environmental variability and life history traits may alter our assumptions about population productivity, and we lay the foundation for a decision based age-structured analysis. In the second chapter, the approach is extended further into the ecological realm by considering how community interactions between Atlantic cod and harp seals can be represented in state space. Our results indicate that since the fishing moratorium in 1992, harp seals have potentially lowered cod productivity, preventing their recovery.

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