Estimating and quantifying statistical uncertainties of bycatch discards in the U.S. West Coast groundfish fishery

The amount of fishery catches discarded at sea often needs to be statistically estimated based on sample data from limited at-sea observations. Any statistical estimates from sample data should be presented with statistical measures of uncertainty or precision, such as variances, standard errors, or coefficient of variation, around the point estimates. While these metrics can be obtained from the applications of fundamental statistical procedures, scientists and managers lack a concise and accessible literature that demonstrates the concepts and derivations of statistical uncertainty formulas for at-sea discard estimates. This article fills that gap by documenting the methods used to compute uncertainty metrics for at-sea bycatch discard estimates in the U.S. West Coast Groundfish Fisheries. Alternative formulas are included to increase usability and minimize errors across different types of data structures. These procedures can support the use of uncertainty metrics in monitoring and management of fisheries globally.