Assessment in salmon and groundfish fisheries

Management of sustainable fisheries requires the development and application of procedures to assess the abundance and productivity of stocks, as well as risks to the fishery. Such assessment takes place in a setting of environmental variability, limited information, uncertainty, and, as exploitation increases, changes in ecosystem structure. In spite of these difficulties, fishery models must provide adequate advice for managers and policy makers. This document addresses several issues in the assessment and management of marine fisheries in the presence of change, uncertainty, and risk.; I first focus on an investigation of risk: the development of a model for the assessment of risk to wild salmon from aquaculture and from escaping aquaculture salmon. This age-structured population dynamics model was developed with the aim of addressing both risk to the wild population and communication of that risk to policy makers and stakeholders in the fishery. Towards that end, the model is embedded in a menu-driven interface, enabling a hands-on investigation of a variety of possible ecological interactions between the species.; I then turn to a method for assessing fishing effort in a mixed-target fishery. Many recreational and artisanal fisheries can shift between habitats (e.g., from fishing onshore to offshore species), and records of catch do not reflect the shift explicitly. This makes calculation of the catch per unit effort (CPUE, an index of abundance) for a particular species difficult. In order to assess the amount of effort that should be included in a species CPUE, a logistic regression technique was employed, using the species composition of catch to infer fishing targets in catch histories from the California recreational fishery. The multispecies method was then used on data simulated to suggest conditions that might occur in the actual fishery, in order to evaluate its effectiveness.