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.

Chesapeake Bay Status:

First Record
Regular Resident

Source Region
Native Region
North America North America

Vector(s) of Introduction
Fisheries(Fisheries Accidental)

History of Spread:

Pylodictis olivaris (Flathead Catfish ) is native to Mississippi and Gulf drainages from PA and ND, south to Gulf, AL to Mexico. Its native range includes a small southern part of Great Lakes drainage (Page and Burr 1991), but it has recently expanded into or has been introduced to Canadian waters of Lake Erie (Goodchild 1993). Releases of P. olivaris on the Atlantic slope were mostly accidental or unauthorized (VA, NC, GA). Pylodictis olivaris has also been introduced to CA, AZ, NM, CO, ID, WA. amd OR. Altogether, P. olivaris has been introduced to non-native drainages in 18 states (Goodchild 1993; Guier et al. 1981; Jenkins and Burkhead 1993; Florida Caribbean Science Center 2001; Page and Burr 1991; Thomas 1993).

Pylodictis olivaris were imported by Virginia Division of Fish and Game (VDIFG) in the 1960s and kept in ponds at Hog Island Game Refuge for research. The first release into the James estuary in 1965 was accidental, due to floods. Pylodictis olivaris were also released, deliberately in the Roanoke drainage to the south. VA populations appear to be established. Although juveniles are rarely caught; sizes of record fishes increased through the 80's (Burkhead et al. 1980; Jenkins and Burkhead 1993). This species seems to have a remarkable ability to start populations from very small stockings (12-50 fish) (Jenkins and Burkhead 1993).

James River- Pylodictis olivaris was accidentally released 1965 at Hog Island Wildlife Refuge (~ 50 fish); a population was established. Catches in the upper James in the Blue Ridge-Allegheny region (starting in 1983) were probably due to a separate, undocumented introduction (Burkhead et al. 1980; Jenkins and Burkhead 1993). Catches of large P. olivaris in the James River were mentioned in ocasionally in fishing columns of the Washington Post in the summers of 1995-2000, though much less frequantly than those of Ictalurus furatus (Blue Catfish).

Potomac River- Twelve P. olivaris were stocked in Occoquan Reservoir, and a population was established (Jenkins and Burkhead 1993). By 2003, according to the Washington Post fishing columns, fishermen were catching them in the mainstem of the Potomac.

Susquehanna River- In July, 2002, several juvenile P. olivaris were caught downriver of Safe Harbor Dam in PA, about 50 km above tidal waters. This species is apparently now established in the river, and can be expected to colonize upper Chesapeake Bay. Fishermen have been asked not to release any fish that they catch. The source of these fish is not known (Pennsylvania Fish and Boat Commission 2002). In 2004, 7P. olivaris were caputrued in the West Fishlift of Conowingo Dam, just above the tidal portion of the Susquehanna (Brown et al. 2005). They are now regularly caught in the tidal Susquehanna and in upper Eastern Shore Tributaries (Garman et al. 2010).

Delaware River- Pylodictis olivaris was first collected in the Blue Marsh reservoir, on the Schuyllkill River, 120 km upstream of Philadelphia PA. This catfish is now established in the Delaware River system (Florida Caribbean Science Center 2002). Currently, this catfish has been collected from the mouth of Delware & Raritan Canal at Lambertville NJ, above the head of tide at Trenton, to Philadelphia (Brown et al. 2005). The fish could have been introduced as a contaminant in a shipment of Ictalurus punctatus (Channel Catfish), but illegal releases by fishermen are much more likely (Brown et al. 2005).

History References - Burkhead et al. 1980; Brown et al. 2005; Florida Caribbean Science Center 2000; Goodchild 1993; Guier et al. 1981; Jenkins and Burkhead 1993; Page and Burr 1991; Pennsylvania Fish and Boat Commission; Thomas 1993

Invasion Comments:

Vector(s) of Introduction- Pylodictis olivaris was stocked in holding ponds at the Hog Island Game Refuge and escaped into James estuary during floods. Subsequent, it was deliberately stocked in Occoquan Reservoir, Potomac drainage (Burkhead et al. 1980). Newly established populations in the Delaware and Susquehanna Rivers may have been introduced with contaminated stocks of Ictalurus punctatus (Florida Caribbean Science Center 2002).

Range Status- This fish is 'expected to spread widely in the James and Roanoke rivers. ...Following establishment, it dispersed rapidly and widely in the Cape Fear River, NC' (Jenkins and Burkhead 1993).

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