Bias in survival estimates from tag-recovery models where catch-and-release is common, with an example from Atlantic striped bass (Morone saxatilis)

Abstract

Survival rate is underestimated when tag-recovery models include tags recovered from harvested and caught-and-released fish. The magnitude of the bias depends on tag-recovery rate, proportion of catch released alive, and reporting rate; changes in these factors over time confound temporal changes in survival. The bias is of potential concern for any tagging study where catch-and-release is mandatory or practiced voluntarily. The bias is of concern particularly for the Atlantic striped bass (Morone saxatilis) tagging study where catch-and-release is common and anglers commonly remove the tag upon capture regardless of fish disposition. Biased estimates of striped bass survival did not change with changes in harvest regulation during the mid-1990s. However, bias-adjusted estimates of survival showed a decrease, which corresponds to the regulatory change made in 1995. Year-specific reporting rate is critical to bias adjustment, underscoring the need for reward tags in fish tagging studies. Tag-recovery modeling allows for a diverse set of models, each of which can produce widely different estimates with far-reaching consequences for management. We applied model averaging to base inference on a weighted average of parameter estimates and to account for model selection uncertainty.