Indirect Estimation of Red Snapper (Lutjanus campechanus) and Gray Triggerfish (Balistes capriscus) Release Mortality

Release mortality was estimated indirectly for red snapper and gray triggerfish in the northern Gulf of Mexico from condition of tagged fish. Condition at release was assessed for tagged red snapper (n = 2,932) and gray triggerfish (n = 842) based upon their swimming behavior. Condition-1 was assigned to fish that oriented toward the bottom and swam down vigorously. Fish in condition-2 oriented toward the bottom but swam erratically. Fish in condition-3 swam very erratically and remained at the surface, while fish in condition-4 were unresponsive and presumed dead. Overall, 86.5% of red snapper and 99.2% of gray triggerfish were released in condition-1. Depth of capture, fish size, and transporting fish prior to release significantly affected red snapper release condition (p < 0.01). Of 550 recaptured red snapper, 98.4% were released in condition-1, while 100% of 160 recaptured gray triggerfish were released in condition-1. Release condition significantly affected recapture rate for red snapper (p < 0.001). Comparisons with reported estimates of release mortality for red snapper indicate that the cumulative percentage of fish released in conditions other than condition-1 may serve as a proxy for acute release mortality. Further research is required to validate this approach; however, it may prove to be a practical method to evaluate release mortality in recreational and commercial fisheries through observer programs.