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Native to the central USA, the Blue Catfish Ictalurus furcatus and the Flathead Catfish Pylodictis olivaris have been widely introduced into many Atlantic slope rivers and are now found in several drainages of the Chesapeake Bay. Fisheries managers are concerned that these large, long‐lived catfish species may be contributing to observed declines in anadromous species, such as the American Shad Alosa sapidissima, Blueback Herring A. aestivalis, and Alewife A. pseudoharengus, all of which once comprised major U.S. fisheries. We assessed spatiotemporal variability and selectivity in the diets of Blue Catfish and Flathead Catfish during the spawning migration of these alosines. Catfish stomachs were collected during March–May in nontidal freshwater, tidal freshwater, oligohaline, and mesohaline portions of the James River. Diet contents were extracted from 2,495 catfish, 69.86% of which had prey items present in their foreguts (N = 1,743). We used DNA barcoding to identify degraded fish prey; nearly 30 taxa that would have otherwise gone undetected were identified in this manner. Blue Catfish had broad, omnivorous diets, whereas Flathead Catfish fed solely on other fish. Alosines were found in 4.46% of Blue Catfish stomachs and 16.67% of Flathead Catfish stomachs. Flathead Catfish selectively preyed on American Shad and, to a lesser degree, river herring. Alosines were consumed more frequently in nontidal freshwater areas, particularly in the high‐gradient reach between Bosher Dam and the 14th Street Bridge, and predation on alosines peaked in April. Our results suggest that Flathead Catfish are likely to have a greater per capita impact on depleted alosines. Furthermore, dams and other obstacles to fish movement may increase alosines’ vulnerability to predation by large catfish.

Native to the central United States, Flathead Catfish Pylodictus olivaris have invaded Atlantic coast rivers from Florida to Pennsylvania. They are now invasive in several subestuaries of the Chesapeake Bay, yet contemporary accounts of their distribution do not exist. Due to their piscivorous nature, Flathead Catfish could have deleterious impacts on native ichthyofauna, yet their feeding ecology has not been well described in these systems. We used a large-scale, stratified random sampling effort to describe the current distribution and feeding ecology of Flathead Catfish in Virginia tidal rivers. Low-frequency electrofishing was conducted at more than 1,500 sites in the James, Pamunkey, Mattaponi, and Rappahannock rivers in eastern Virginia, resulting in 766 Flathead Catfish being captured in the James, Pamunkey, and Mattaponi rivers. Flathead Catfish are abundant in the tidal James River from Richmond, Virginia, to the confluence of the Chickahominy River. A relatively new but established population was also observed in the Pamunkey River, where the highest observed densities of Flathead Catfish occurred near Williams Landing (37°36 0 21.49″N, 77°5 0 33.42″W) in New Kent County, Virginia. Stomachs collected from 731 Flathead Catfish revealed that they are piscivores that feed heavily on Gizzard Shad Dorosoma cepedianum, White Perch Morone americana, and various Alosa species. Analysis of trophic level, diet breadth, and feeding strategy demonstrated that Flathead Catfish are piscine specialists that occupy trophic positions indicative of an apex predator. Our results show that Flathead Catfish could have substantial per capita impacts on at-risk native species including American Shad Alosa sapidissima, Blueback Herring A. aestivalis, and Alewife A. pseudoharengus as they make seasonal migrations in and out of these river systems. Moreover, future range expansion of Flathead Catfish into the Rappahannock River is plausible, as established populations now exist in adjacent tributaries.

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