Evaluating quantitative fatty acid signature analysis (QFASA) in fish using controlled feeding experiments

Accurate diet estimation has long been a challenging issue for researchers investigating predators because of constraints associated with stomach content analyses. Fatty acid signature analysis offers an alternative avenue to study long-term diet trends in consumers. Despite the wealth of experiments involving fatty acids of fish and their diets, few have evaluated quantitative fatty acid signature analysis (QFASA) with fish consumers. To this end, we fed juvenile lake trout (Salvelinus namaycush), round goby (Neogobius melanostomus), and yellow perch (Perca flavescens) various invertebrate species and back-classified each predator to its respective prey using only fatty acids. Estimates were highly accurate when metabolism of diets was natively accounted for by using fatty acid profiles of predators fed known diets as the “prey library”. While highly accurate results were obtained, accounting for each predator-prey relationship limits the use of QFASA to predators that consume a limited number of species. We call for specific knowledge as to how fatty acid profiles reflect each predator-prey interaction before attempting to use fatty acids to quantify a consumer’s diet. Only after incorporating such data will QFASA provide an accurate view of individual’s diets when stomach content data are not available or are invalid.