Research Document - 2000/149

Reconstructing the Offshore Pandalus jordani Trawl Fishery off the West Coast of Vancouver Island and Simulating Alternative Management Policies.

By S. Martell, J. Boutillier, H. Nguyen, and C. Walters

Abstract

Shrimp trawl fisheries in Pacific Fishery Management Areas 124 and 125 have historically been a boom or bust fishery. The authors use research data and commercial catch and effort data to reconstruct the Pandalus jordani stocks off the WCVI and examine stock-recruitment relationships, changes in catchability, and fishing power differences between two separate research vessels, the GB Reed and the WE Ricker. The authors then use the results of the population reconstruction to develop and parameterize a simulation model for exploring four alternative management policies for this fishery. The results of the population reconstruction suggest that recruitment, in years of low spawning biomass, may be in the form of immigration; however, using a synthesis approach to reconstructing the population suggest there is a clear stock-recruitment relationship. Survey biomass estimates from annual research surveys are good predictors of pre-season vulnerable biomass, and in conjunction with a formal stock assessment model could be used to calculate annual total allowable catches. The authors also found that catchability had increased over the last 10 years, however, they are uncertain whether these changes are due to range collapse or improvements in fishing technology. Simulation results suggested that there were no long-term or short-term gains to be made by aggressively managing this fishery. To maintain an economically viable fishery, the authors suggest a cautious approach to management. The fishery in areas 124-5 should be closed in years when estimated biomass is less than 1,000 tonnes, and a maximum exploitation rate of 35% when the biomass exceeds 1,000 tonnes. The authors also suggest that consideration be given to setting up a quota-based management system in which annual TAC is based on pre-season stock estimates.

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