Chesapeake Bay Introduced Species Database

Pylodictis olivaris

Common name(s):
Flathead Catfish
Flathead Catfish are giant fish (up to 60 inches, 130 lbs), and very popular among anglers because of their size and tastiness. They are native to Mississippi and Gulf drainages. These catfish have been stocked or otherwise released into drainages in 18 states. The first Chesapeake release in 1965 was accidental; the Virginia Division of Fish and Game was keeping them in ponds on Hog Island Game Refuge for research when about 50 fish escaped into the James River during a flood. Although only a few fish were released at that time they established sustaining populations. Similarly, only 12 fish were stocked in the Occoquan Reservoir, but that was enough to establish a population. Populations of flathead catfish have been found in many other areas of the Chesapeake watershed, including the Susquehanna River, and it is suspected that small numbers of fish were released by anglers due to their popularity as a sport fish. This species? ability to colonize river systems, as well as its role as a top predator with an enormous appetite, means that unauthorized stockings by fisherman are a serious problem.
Image courtesy of Eric Engbretson, U.S. Fish and Wildlife Service.

Economic Impacts

Economic impacts of Pylodictis olivaris have not been reported from the Chesapeake Bay watershed, and might have been limited by low abundance in invaded tributaries (Jenkins and Burkhead 1993). 'Good flavor and large size have made the flathead catfish popular among anglers.' (Jenkins and Burkhead 1993). Catches of several large fish in the James River were mentioned in fishing columns of the Washington Post in the summer of 1995. Ictalurus furcatus (Blue Catfish) appears to be much more abundant and more frequently caught in the James (Jenkins and Burkhead 1993), and is more frequently mentioned by name in newspaper fishing reports.

References - Jenkins and Burkhead 1993

Economic Impacts Outside Chesapeake Bay

Pylodictis olivaris (Flathead Catfish) is a popular sportfish because of its spectacular size. However, in a number of U.S. rivers, negative impacts are well documented (Fuller et al. 1999). Examples include the Cape Fear River, NC (Guier et al. 1981) and the Altmaha River, GA (Thomas 1993) and other GA rivers (Fuller et al. 1999). Rapid proliferation of P.olivaris and intense predation has led to a decline of smaller, more catchable centrarchids (sunfishes, crappies) and bullheads (Ameirus spp.). Pylodictis olivaris, while an attractive sportfish, are caught by fewer fisherman (Thomas 1993). This fish should probably be regarded as a risky introduction. This species attractions as a sportfish and its apparent ability to colonize river systems from very small stockings (11-50 individuals) means that unauthorized stockings by fisherman are a serious problem (Guier et al. 1981; Thomas 1993). Pylodictis olivaris has been introduced to non-native drainages in 18 states (Fuller et al. 1999).

References- Fuller et al. 1999; Guier et al. 1981; Jenkins and Burkhead 1993; Thomas 1993.

Ecological Impacts

Impacts on Natives:
Competition; Predation
Impacts of Pylodictis olivaris (Flathead Catfish) in Chesapeake Bay appear to be increasing as the population and range of this predator spreads (Garman et al. 2010). Negative effects of introduction in the James River were not noted by Jenkins and Burkhead (1993). However, the effects of introduced predatory catfishes [Ictalurus punctatus (Channel), Ictalurus furcatus (Blue), and P. olivaris) on Alosa sapidissima (American Shad) are being studied in the James River (Garman 1999, pers. comm.). Introductions to the Cape Fear River, NC (Ashley and Buff 1987; Guier et al. 1981) and the Altmaha River, GA (Thomas 1993), and several other GA rivers (Fuller et al. 1999) have had dramatic effects on fish communities, eliminating or drastically reducing abundance of many middle-level predators such as Ameiurus spp. (bullheads and White Catfish), and Lepomis spp. sunfishes.

Competition - Introduction of Pylodictus olivaris led to decline of other fishes, especially catfishes in NC (Guier et al. 1981). However, the frequency of the large Ictalurus furcatus (Blue Catfish) in the stomachs suggests that the earlier decline of native Bullheads (Amieurus spp. before the study was probably due to predation rather than competition.

Predation - Guier et al. (1981) found a wide variety of fishes in stomach contents of P. olivaris, especially catfishes and centrarchids. Ashley and Buff (1987) noted heavy predation on adult A. sapidissima) during their migration in March and April. Other catfish, including native Amieurus catus (White Catfish), were a major food item. Native Bullheads (Amieurus nebulosus (Brown Bullhead); A. natalis (Yellow Bullhead); A. brunneus (Snail Bullhead) were rarely seen in stomach contents, having apparently been greatly reduced earlier by P. olivaris' predation (Guier et al.1981; Ashley and Buff 1987). Thomas (1993) found that P. olivaris' introduction in the Altmaha River, GA was followed by a dramatic decline in Amieurus spp. and Lepomis auritis (Redbreast Sunfish). There is not much information on the impact of P. olivaris on estuaries, but Ashley and Buff (1987) listed 'crabs' and Paralichthys lethostigma (southern flounder) among the prey found.

References - Ashley and Buff 1987; Fuller et al. 1999; Garman 1999, personal communication; Guier et al. 1981; Jenkins and Burkhead 1993; Thomas 1993.
Impacts on Non-natives:
Competition; Predation
Negative effects of the Flathead Catifish's introduction on other introduced species, in the James River were not noted by Jenkins and Burkhead (1993).

Competition - Competition with introduced Ictalurus punctatus (Channel Catfish) and I. furcatus (Blue Catfish) is possible, but predation appears to have been a more important factor in their decline in the Cape Fear River, NC; based on the high frequency of I. furcatus in the stomachs (Ashley and Buff 1987; Guier et al 1981).

Predation - Pylodictis olivaris is not specifically reported to feed on Corbicula fluminea (Asian Freshwater Clam, but did feed to some extent on bivalves. It is an important predator on the introduced catfish I. punctatus and I. furcatus and the centrarchids Lepomis macrochirus (Bluegill), L. microlophus (Redear Sunfish), and Pomoxis nigromaculatus (Black Crappie) in the Cape Fear River, NC (Ashley and Buff 1987; Guier et al. 1981).

References - Ashley and Buff 1987; Guier et al. 1981.

This data was last modified on Friday, February 25th, 2011.
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