Use of a mark-recapture model to evaluate largemouth bass delayed tournament mortality

Abstract

Estimating fishing mortality, including initial and delayed mortality, is necessary to assess potential effects of catch and release tournament fishing events. Previous studies retaining angler-caught fish are useful in understanding delayed mortality but have associated limitations. As an alternative to tournament mortality studies, we estimated daily apparent survival rates of largemouth bass Micropterus salmoides using a modified Cormack-Jolly-Seber model in Program MARK to test for the duration of delayed tournament mortality and to identify important covariates affecting survival. Multiple monotonic trends were evaluated to test acute (2, 3, 4, or 7 d) and chronic (15 or 30 d) delayed mortality hypotheses. The most supported models revealed an acute trend in survival following tournament capture but no support for chronic mortality. Largemouth bass survival decreased with increases in water temperature and the number of tournament capture events. Combined, these factors resulted in up to 90% cumulative mortality at temperatures of 18.8 °C for individuals captured at five tournament events. Our results confirm the potential for high delayed mortality associated with catch and release fishing tournaments. Using mark-recapture data to understand tournament fishing mortality can be a valuable tool in managing highly fished systems.