Unwanted Guests and Stomach Contents: Trophic Dynamics of Sympatric Native (White Catfish Ameiurus catus) and Non-Native (Blue Catfish Ictalurus furcatus) in Chesapeake Bay

The rapid range expansion and increase in abundance of non-native Blue Catfish Ictalurus furcatus in upper Chesapeake Bay (CB) have raised serious management concerns, particularly as it has been linked with declines of native White Catfish Ameiurus catus in Virginia. To investigate the relative abundance and trophic dynamics of ictalurid catfish in upper CB, tidal fresh areas within Nanticoke, Patuxent, Sassafras, and Susquehanna River systems were sampled during summer/fall 2012 and 2013 using boat electrofishing. The stomach contents of 319 Blue Catfish and 261 White Catfish were examined and all prey items were identified to the lowest taxonomic level. Important prey items included amphipods, chironomid larvae, trichopterans and other insects, bivalves (predominantly Corbicula fluminea), and fish. Multivariate analysis of catfish stomach contents indicated significant spatial differences within species, but considerable overlap between species’ diets, except that Blue Catfish ingested greater amounts of fish prey than White Catfish, particularly at larger sizes. DNA Barcoding of gut contents identified 23 fish species (21 from Blue Catfish and 5 from White Catfish), including species undergoing active restoration efforts (e.g., Alosa spp.), and commercially important species, e.g., Striped Bass Morone saxatilis, White Perch Morone americana, American Eel Anguilla rostrata and Menhaden Brevoortia tyrannus.