A Novel Approach for Mitigating Depredation, a Source of Cryptic Fishing Mortality for Gulf of Mexico Red Snapper Lutjanus campechanus

Knowledge of species interactions within marine fisheries can lead to a more holistic approach to management. While some interactions (e.g. trophic) are intuitive, others are more subtle. Depredation, the partial or complete removal of hooked fish from fishing gear by non-target species, is a source of cryptic fishing mortality. In the Gulf of Mexico, recent increases in Red Snapper (Lutjanus campechanus) depredation have been reported, straining a fishery already under strict regulation; unfortunately, mitigating these harmful effects requires identifying the species responsible for depredation, a task with clear logistic difficulties. Given the strong economic and ecologic consequences of this unique interaction, we developed an exciting, new technique to identify the depredating species from residual levels of DNA left on the damaged fish. Using video and field evidence of actual depredation events, we confirmed that our PCR strategy can accurately and definitively determine the depredator responsible for Red Snapper mortality. These findings present the development of a powerful new tool for positively identifying depredating species, a critical precursor to successful depredation mitigation.