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UBC Theses and Dissertations

Optimal harvest policies in salmon gauntlet fisheries : terminal versus mixed stock fishery harvest Luedke, Wilfred Harold


A case study of the chum salmon (Oncorhynchus keta) gauntlet fisheries in Southern British Columbia is described. Acrimony between industry and government managers has been commonplace in the management of this fishery. In an attempt to alleviate this acrimony, a management system call the "clockwork" has been implemented, which provides all fishermen an opportunity for greater understanding of the management rationale and greater input into the decision-making process. The clockwork has been generally successful; the stocks are rebuilding and the fishermen are involved in the management of the fishery. However, two problems are identified in the clockwork. First, the success of the clockwork in alleviating the aaimony associated with the chum fishery depends on the ability of fishery managers to provide sound and scientifically defensible in-season stock assessments. If the assessments have no better track record than the intuition of managers and fishermen then the clockwork will not be successful. Second, there is a nagging problem of allocation of harvests between the mixed stock fishery in Johnstone Strait and the terminal fishery in the Fraser River. The main factor is the difference in price behveen the two fisheries; the price in the terminal fishery is only about one-third of the price paid in the mixed stock fishery, Dynamic programming techniques are used to determine the optimal harvest strategies for this gauntlet fishery. Generally, the optimal strategy is similar to a fixed escapement strategy when both stocks are equally abundant. But when one stock is much more abundant the optimal strategy is to harvest harder in the mixed stock fishery. With the current difference in value per fish between the two fisheries, the optimal exploitation rates in the terminal area are zero, all the catch is taken in the mixed stock fishery. The minimum price at which terminal fisheries provide long term economic benefit is the threshold price. For the parameters used to describe the current fishery, the threshold price is approximately 40% of the mixed stock fishery price. Furthermore, the threshold price differs with stock recruitment parameters, especially stock productivity and recruitment variability. Generally the more similar the stocks are, with respect to stock and recruitment characteristics, the lower the threshold value for fishing in the terminal areas. The results provide a basis for discussion of the utility of terminal fisheries, and by adjusting the relative value of the terminal fishery in relation to the mixed stock fishery can incorporate additional social and aesthetic values, as well as costs such as harvesting costs and fisheries management costs.

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