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 are important in light of recent catch reconstructions. If catch is over-estimated, this could lead to thinking the population is doing better than it really is, and recommending harvest limits greater than would be sustainable.
Merrill Rudd, graduate student in the UW School of Aquatic and Fishery Sciences, will be Friday’s speaker from 12:30-1:30 in FSH 203.
This Friday we will also begin streaming seminars via GoToMeeting. To join the seminar remotely, please use this link: https://global.gotomeeting.com/join/132865341
Title: Does unreported catch lead to overfishing?