A Monte Carlo simulation model of the commercial gillnet fishery for sockeye salmon (Oncorhynchus nerka) returning to the Skeena River, British Columbia, is used to evaluate the benefits of forecasts of annual returns of sockeye salmon based on test fishery and commercial fishery data. The test fishery is economically efficient, its net annual benefit is between $234,000 and $544,000. In the sensitivity analysis of the results, benefit decreased to equal cost only when the current variance of the pre-season forecast of returns was reduced by 75%. The benefit of test fishery information would be difficult to detect using actual data because the improvement in mean annual catch is small relative to the variability in annual catch. This problem of detectability could lead to termination of fishery management initiatives that are, on average, economically efficient.