Yield-per-recruit modeling of a British Columbia intertidal clam fishery : management implications of sampling design, variable recruitment, and data collection by user group

Invertebrate fisheries are becoming increasingly important in British Columbia (B.C.), but setting robust management strategies is difficult due to lack of data for stock assessment and poor understanding of invertebrate population dynamics. I applied Monte Carlo simulation to a butter clam (Saxidomus giganteus) fishery at Seal Island (near Courtenay, Vancouver Island, B.C.) to evaluate the effects of sampling methods, sample size, parameter estimation method, and variable recruitment on the accuracy and precision of input parameters to the Beverton-Holt yield-per-recruit (Y/R) model. The effects of this accuracy and precision on setting management strategies such as minimum legal size (MLS) with the Y/R model were evaluated by calculating the expected loss of Y/R and fishery value for each model scenario. Scenarios used one of four sampling methods, three methods of estimating total instantaneous mortality (Z) (Hoenig's method, Beverton-Holt method, and catch-curve analysis), and four levels of recruitment variability (including constant recruitment).