Does Unreported Catch Lead to Overfishing?

It is generally believed that unreported catch has a negative impact on fish stock status and management. While unreported catch certainly obscures our understanding of a fishery’s dynamics, this study examines its impact on our ability to estimate stock status and sustainable catch limits. We conducted a simulation study that generated an abundance index and catch time series from a “true” population, and then estimated the population’s carrying capacity and maximum sustainable yield (MSY) using a Pella-Tomlinson surplus production model. We compared results between four scenarios of catch misreporting: constant under-reporting, increasing reporting rate, decreasing reporting rate, and constant over-reporting (to represent an over-estimated reconstructed catch). For all scenarios of catch under-reporting, we under-estimated carrying capacity, population size, and MSY on average. Alternatively, over-estimating reconstructed catch led to over-estimates of MSY. These results suggest that a manager blind to under-reported catch would likely recommend more conservative harvest limits on average. These results are only applicable to total allowable catch-based management where both catch and an abundance index are available. However, our findings suggest that increasing the reporting rate would likely increase equity for fishermen via an increased catch limit, while there may danger to sustainable management in over-estimating reconstructed catch.