MODELING NORTHERN ABALONE, HALIOTIS KAMTSCHATKANA, POPULATION STOCK AND RECRUITMENT IN BRITISH COLUMBIA

Abstract

The northern abalone, Haliotis kamtschatkana, fisheries in British Columbia (BC) were closed in 1990 because of substantial declines in the stock biomass. Abalone biomass has remained low since the fishery closure. We used abalone survey data and established growth models to study the stock-recruitment (SR) relationships, estimate mortality rates, and simulate population growth trajectories at various mortality levels for abalone populations in the Queen Charlotte Islands and the Central Coast of BC. The fitted SR curves were flat and near linear, indicating a lack of productivity in the abalone populations. At low spawning stock biomass (<0.05 kg/m2) the SR relationships appeared to be density independent. Annual mortality rates (Z) were estimated to be 0.29–0.36, which included natural mortality and poaching rates. Simulation studies showed that abalone population growth was sensitive to mortality rates. The abalone populations would be sustainable with Z around 0.25, and would increase or decrease with lower or higher Z, respectively. To rebuild the northern abalone populations, measures need to be taken to minimize or eliminate poaching to reduce mortality rates.