Midwest Fish & Wildlife Conference 2019

AUTHORS: Aaron P. Maloy, Stephanie Dowell, Roman Crumpton, James Henne, Julie C. Schroeter, Christopher B. Rees, Meredith L. Bartron – U.S. Fish & Wildlife Service

ABSTRACT: Flathead catfish (Pylodictis olivaris) are large, primarily piscivorous, predators native to Gulf Coast drainages of the Mobile, Mississippi and Rio Grande River.  Intentional stockings outside of their native range were common in the early to mid-20^th century, many of which resulted in self-recruiting populations that have become invasive.  Flathead catfish alter native species communities through direct predation and are considered one of the most biologically harmful invasive fish. Obtaining detailed trophic data through traditional dietary analysis is difficult due to the lack of morphological characteristics of prey and because fish are commonly taken with empty stomachs. To address these challenges a study was undertaken on the Edisto River, South Carolina to assess the trophic ecology of invasive flathead catfish using DNA-based dietary methods. A combination of DNA barcoding and metabarcoding revealed a varied diet of crustaceans, bivalves, eggs and numerous fish species.  Traditional COI barcoding was useful for determining the identity of larger remnants of prey items of both fish and invertebrates.  Metabarcoding of the 12S rRNA gene targeted fish species and was successful at identifying prey even when morphological examination determined stomachs to be empty.  A higher rate of prey detection was observed in material collected from the stomachs than that obtained from the intestines.  Used in conjunction, the two methods provided a more complete understanding of flathead catfish predation than any one method in isolation.