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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: Flathead Catfish

Taxonomy: available through www.itis.gov

Identification: Projecting lower jaw, pale tips on tail fin, short anal fin.  Becker (1983); Page and Burr (1991); Etnier and Starnes (1993); Jenkins and Burkhead (1994).

Size: 155 cm (Page and Burr 1991)

Native Range: Lower Great Lakes and Mississippi River basins from western Pennsylvania to White-Little Missouri River system, North Dakota, and south to Louisiana; Gulf Slope from Mobile Bay drainage, Georgia and Alabama, to Mexico (Page and Burr 1991).

Native to Lake Erie and tributaries to Lake Erie and Lake Michigan (Hocutt and Wiley 1986).

Ecology: According to the Pennsylvania Fish and Boat Commission (2003), P. olivaris is found in large rivers, streams, and lakes, usually over hard bottoms. They prefer deep, sluggish pools, with logs and other submerged debris that can be used as cover. Young P. olivaris live in rocky or sandy runs in the river and in riffles, often under stones on riffles (Hubbs et al. 2004).

Unlike other catfish, Flathead Catfish feed on only live prey.  Adult Flathead Catfish are piscivorous ambush predators.  Many feeding studies have found that Pylodictis olivaris prey heavily on sunfish (Lepomis spp.). One study also found that they reduced the number of common carp (Cyprinus carpio) and bullheads (Ameiurus spp.). However, the introduced population in the Flint River system was found to prey largely on crayfish, and it was also found that young-of-the-year P. olivaris fed on darters (Etheostoma spp.) clupeids, catostomids, ictalurids, and centrarchids.

Age at sexual maturity appears to be regionally dependent, ranging from 3-5 years for males and 3 to 7 years for females.  Spawning occurs in late spring when water temperatures reach 21 to 27 degrees celsius. One or both parents excavate a nest that is usually made in a natural cavity or near a large submerged object. Females lay a mass of up to 100,000 eggs. Males guard the nest and agitate the eggs to keep them clean and aerated. The young remain in a school near the nest for several days after hatching, but soon disperse.  Flathead Catfish can live up to 28 years.

Means of Introduction: The Flathead Catfish has been intentionally stocked in most cases. In Idaho, however, flatheads were accidentally stocked instead of blue catfish (Simpson and Wallace 1978). Populations in the Apalachicola River, Florida, probably spread from introductions upstream in the Flint River, Georgia. It is believed that flatheads were stocked by anglers circa 1950 in the vicinity of Potato Creek in Upson County, Georgia, with stock from the Tennessee drainage (Quinn 1988). They were recorded in the Flint River below the Warwick Dam at Lake Blackshear in the early 1960s, and at Albany in the early 1970s (Quinn 1988). The species was apparently first stocked in the Cape Fear River in 1966 when 11 sexually mature fish were released near Fayetteville, North Carolina, by North Carolina Wildlife Resources Commission biologists (Guire et al. 1984; Ashley and Buff 1986). Flatheads were stocked in Atlantic drainages (Savannah and Altamaha) in Georgia in the 1970s (Bart et al. 1994; C. Jennings, personal communication). According to Bart et al. (1994), at least some of these were the result of stocking by Georgia Department of Natural Resource personnel. The first known reports of this fish in California were recorded catches made in the lower Colorado River near Yuma in 1966 (Dill and Cordone 1997). The Colorado River populations in California and Arizona resulted, at least in part, from a stocking of about 600 Flathead Catfish above Imperial Dam made by the Arizona Game and Fish Department in 1962 (Dill and Cordone 1997). According to Dill and Cordone (1997), the believed route of the Flathead Catfish was downstream to Imperial Dam and subsequently into the All American Canal system to the Imperial Valley. Minckley (1973) reported that the species was introduced prior to 1950 into the Gila River system, a tributary of the Colorado River; however, Dill and Cordone (1997) indicated that, as far as is known, the Flathead Catfish was not taken in the lower Colorado River basin until after 1962. A single fish was taken 20 November 1995 in Arizona from the upper San Pedro River, about 32 kilometers from the Mexican border (S. Stefferud, personal communication). It is not known how the species gained access to the upper reach of this river. In Wisconsin, flatheads probably entered the Wolf and Fox drainages via the canal at Portage (Becker 1983). The Ochlockonee River introduction in Florida and Georgia was probably due to illegal stocking by anglers with fish from the nearby Apalachicola River, where the fish had also been introduced. The flathead's presence in eastern Pennsylvania is most likely due to stock contamination of channel catfish shipments (M. Kaufman, personal communication).

Status: The Flathead Catfish has become established in most waters where introduced. For instance, it is widespread and reproducing in the lower Colorado River basin (Dill and Cordone 1997). As of about 1980, the Cape Fear River population had expanded from the site of its initial release near Fayetteville, North Carolina, and was found to inhabit a 201-kilometer stretch of the river (Guire et al. 1984). In samples taken by Guire et al. (1984) from the Cape Fear River, flathead accounted for 10.52% of total fish numbers and 64.7% of total fish weight. Establishment in Oregon is uncertain (Bond 1994). The species does not appear to have survived to reproduce in Wyoming (Hubert 1994). It has been reported from the San Pedro River, Arizona, and from the Suwannee River, Florida. Established in Blue Marsh Reservoir and the Schuylkill River in Pennsylvania; reported in Springton Reservoir, Pennsylvania.

Impact of Introduction: Many feeding studies have found that Flathead Catfish prey heavily on sunfish Lepomis spp. (Quinn 1988). One study found that they reduced the number of common carp Cyprinus carpio and bullheads Ameiurus spp. (Quinn 1988). However, the introduced population in the Flint River system was found to prey largely on crayfish, and that young-of-the-year flatheads fed on darters Etheostoma spp. clupeids, catostomids, ictalurids (including other flatheads), and centrarchids were also consumed (Quinn 1988). According to Quinn (1988), introduced flatheads in the Flint River rely more on crayfish than any other catfish population yet described. A severe decline in native fish species, particularly native bullhead species, was observed in the Cape Fear River within 15 years of the first Flathead Catfish introduction (Guire et al. 1984; Jenkins and Burkhead 1994). Feeding studies conducted in the Cape Fear River showed that flatheads consume mainly bullheads, catfishes, shad, and sunfishes (Guire et al. 1984; Ashley and Buff 1986). In 1979, flatheads in the Cape Fear River fed primarily on bullheads. However, by 1986, bullhead populations had declined and Flathead Catfish had switched to preying on shad (Ashley and Buff 1986). Diet studies also have been conducted in the Oconee River in Georgia, where this catfish had been implicated in causing declines of native bullheads and sunfishes (especially redbreast sunfish Lepomis auritus). However, findings of that initial study were inconclusive since most of the Flathead Catfish examined had empty stomachs (C. Jennings, personal communication). Flathead Catfish also may be responsible for declines in other native species in the Altamaha drainage (C. Jennings, personal communication). In the Ocmulgee River, Georgia, abundances of silver redhorse Moxostoma anisurum, robust redhorse M. robustum, snail bullhead Ameiurus brunneus, flat bullhead A. platycephalus, and redbreast sunfish Lepomis auritus, were negatively correlated with Flathead Catfish occurrence and abundance (Bart et al. 1994). This correlation may be due to direct predation. Several authors have reported suckers and catfish as common prey items of flatheads (Bart et al. 1994). The snail bullhead and flat bullhead appear to be most affected by the presence of Flathead Catfish in the Ocmulgee drainage (Bart et al. 1994). It is suspected flatheads may be contributing to the decline of the federally threatened Gulf sturgeon Acipenser oxyrinchus desotoi by consuming the young benthic fish in the Apalachicola River (J. Williams, personal communication). The Flathead Catfish is thought to be contributing to the decline of the razorback sucker Xyrauchen texanus. For instance, Marsh and Brooks (1989) found that intensive predation by Flathead Catfish and channel catfish on juvenile razorback suckers is likely to prevent hatchery transplants of this southwestern endangered sucker from becoming re-established in portions of its natural range. If the Flathead Catfish becomes established in the San Pedro River, it could mean a major loss for recovery of several species (S. Stefferud, personal communication). Introductions of Flathead Catfish are probably the most biologically harmful of all fish introductions in North America (C. Gilbert, personal communication). Flathead Catfish, along with other nonnative piscivorous fishes, have been shown to reduce the abundance and diversity of native prey species in several Pacific Northwest rivers (Hughes and Herlihy 2012).

Remarks: The Flathead Catfish became the dominant predator in the Cape Fear drainage of North Carolina within 15 years of the introduction (Guire et al. 1984). The species may actually be native to the upper Tennessee drainage in North Carolina (Jenkins and Starnes, personal communication). In their book on Alabama fishes, Mettee et al. (1996) presented conflicting information regarding native versus introduced ranges. These researchers stated, in the species account, that Pylodictis olivaris is introduced to the Conecuh and Escatawpa river systems, but they listed the species as "native" in their summary table. Starnes et al. (2011) suggest that although the Potomac River population is highly localized, favorable habitat in the Plummers Island area could allow it to expand further upstream.

University of Michigan voucher specimens are in Bailey et al. (2004) for two tributaries in southern Michigan. A single specimen was caught in the Canadian waters of western Lake Erie in 1978 by a commercial fisherman. This specimen was deposited in the Royal Ontario Museum collection (Crossman and Leach 1979).

Despite the fact that Wydoski and Whitney (2003) say Flathead Catfish were in the lower Snake and Columbia rivers by the mid 1970s, neither the regional fishery biologist for that area, nor the warmwater fisheries manager for the state have ever seen or heard of one in the state (Chris Donnelly and Bruce Bolding, Washington Department of Fish and Wildlife, personal communication 1/6/2016, 1/7/2016). Although there is a supposed Washington State Record fish (22.8 lbs from the Snake River in 1981 ({Game, 2016c #11074})), Bolding believes this was a misidentified Channel Catfish.

References: (click for full references)

Anonymous 2001. Oregon's Warm Water Fishing with Public Access. [online]. URL at http://www.dfw.state.or.us/warm_water_fishing/index.asp.

Anonymous. 2004. Idaho warm water fish.  Idaho Fish n Hunt.  Available at URL http://www.idfishnhunt.com/warmwatermenu2.html.

Ashley, K. W., and B. Buff. 1986. Determination of current food habits of flathead catfish in the Cape Fear River. Final Report Submitted to the North Carolina Wildlife Resources Commission, Division of Boating and Inland Fisheries, Raleigh, NC. 19 pp.

Bailey, R.M., W.C. Latta, and G.R. Smith. 2004. An atlas of Michigan fishes with keys and illustrations for their identification. Miscellaneous Publications of the University of Michigan Museum of Zoology 192:1-215. http://deepblue.lib.umich.edu/handle/2027.42/56435.

Baker, B. 1993. Flatheads come to Florida. Florida Game and Fish, June 1993:28--31, 60--61.

Bart, H. L., M. S. Taylor, J. T. Harbaugh, J. W. Evans, S. L. Schleiger, and W. Clark. 1994. New distribution records of Gulf Slope drainage fishes in the Ocmulgee River system, Georgia. Southeastern Fishes Council Proceedings, No. 30:4--9.

Bauers, S. Officials confirm N.J. catch was dreaded flathead. The Philadelphia Inquirer. August 26, 2004.

Becker, G. C. 1983. Fishes of Wisconsin. University of Wisconsin Press, Madison, WI.

Bottroff, L., J. S. St. Amant, and W. Parker. 1969. Addition of Pylodictus olivaris to the California fauna. California Fish and Game 55(1):90.

Brown, J., J Perillo, T Kwak, R Horowitz. 2005.  Implications of Pylodictis olivaris (flathead catfish) introduction into the Delaware and Susquehanna drainages.  Northeastern Naturalist.  12/4:473-484.

Burgess, G. - Florida Museum of Natural History, Gainesville, FL.

Dahlberg, M. D., and D. C. Scott. 1971a. The freshwater fishes of Georgia. Bulletin of the Georgia Academy of Science 29:1--64.

Dahlberg, M. D., and D. C. Scott. 1971b. Introductions of freshwater fishes in Georgia. Bulletin of the Georgia Academy of Science 29:245--252.

Ellis, M. M. 1974. Fishes of Colorado. University of Colorado Studies, Boulder, CO 11(1):1--136.

Etnier, D. A., and W. C. Starnes. 1993. The fishes of Tennessee. University of Tennessee Press, Knoxville, TN.

Fletcher, D. - Warmwater Fisheries Resource Manager, Washington Department of Wildlife, Olympia, WA. Response to NBS-G nonindigenous questionaire and other reports. 1992.

Gilbert, C. - Florida Museum of Natural History, Gainesville, FL.

Guire, C. R., L. E. Nichols, and R. T. Rachels. 1984. Biological investigations of flathead catfish in the Cape Fear River. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 35(1981):607--621.

Hocutt, C.H., R.E. Jenkins, and J.R. Stauffer, Jr. 1986. Zoogeography of the Fishes of the Central Appalachians and Central Atlantic Coastal Plain. 161-212 in C.H. Hocutt and E.O. Wiley, eds. The Zoogeography of North American Freshwater Fishes. John Wiley and Sons, New York, NY.

Hubbs, C.L. and K.F. Lagler.  2004.  Fishes of the Great Lakes region.  Revised Edition.  University of Michigan, Ann Arbor, MI.

Hubert, W. 1994. Exotic fishes. Pages 158-174 in Parish, T.L., and S.H. Anderson, eds. Exotic species manual. Wyoming Game and Fish Department. Laramie, WY.

Hughes, R.M. and A.T. Herlihy. 2012. Patterns in catch per unit effort of native prey fish and alien piscivorous fish in 7 Pacific Northwest USA rivers. Fisheries 37(5):201-211.

Idaho Fish and Game. 1990. Fisheries Management Plan 1991-1995. Appendix I - A list of Idaho fishes and their distribution by drainage.  Idaho Fish and Game.

Jenkins, R.E., and N.M. Burkhead. 1994. Freshwater Fishes of Virginia. American Fisheries Society, Bethesda, MD.

Linder, A.D. 1963. Idaho's alien fishes. Tebiwa 6(2):12-15.

Marsh, P.C. and J.E. Brooks. 1989. Predation by Ictalurid catfishes as a deterrent to re-establishment of hatchery-reared razorback suckers. Southwestern Naturalist 34(2):188-195.

Page, L.M., and B.M. Burr. 1991. A Field Guide to Freshwater Fishes - North America North of Mexico. Volume 42. Houghton Mifflin Company, Boston, MA.

Page, L.M., and B.M. Burr. 2011. A Field Guide to Freshwater Fishes of North America North of Mexico, Second Edition.  Houghton-Mifflin Harcourt. New York, NY.

Quinn, S.P. 1988. Stomach contents of flathead catfish in the Flint River, Georgia. Proceedings of the Annual Conference Southeastern Association of Fish and Wildlife Agencies 41:85-92.

Starnes, W.C., J. Odenkirk, and M.J. Ashton. 2011. Update and analysis of fish occurrences in the lower Potomac River drainage in the vicinity of Plummers Island, Maryland—Contribution XXXI to the natural history of Plummers Island, Maryland. Proceedings of the Biological Society of Washington 124(4):280-309.

State of Oregon. 2000. Warm Water Game Fish Records. 7 pp.

Stefferud, S. - U.S. Fish and Wildlife Service, Arizona Ecological Services Office, Phoenix, AZ.

Sublette, J. E., M. D. Hatch, and M. Sublette. 1990. The fishes of New Mexico. New Mexico Department of Game and Fish, University of New Mexico Press, Albuquerque, NM. 393 pp.

Tomelleri, J. R., and M. E. Eberle. 1990. Fishes of the Central United States. University Press of Kansas, Lawrence, KS. 226 p.

Walker, P. - Maine Department of Inland Fisheries (formerly); Colorado Division of Wildlife, Brush, CO (currently).

Williams, J. - U.S. Geological Survey (retired)

Wydoski, R.S., and R.R. Whitney. 1979. Inland Fishes of Washington. University of Washington Press Seattle, WA.

Wydoski, R.S., and R.R. Whitney. 2003. Inland Fishes of Washington. Second Edition. American Fisheries Society, Bethesda, MD in association with University of Washington Press, Seattle, WA.

Yerger, R. W. 1977. Fishes of the Apalachicola River. Florida Marine Research Publications 26:22-33.

Other Resources:
Flathead catfish at the Fort Worth Zoo

Pennsylvania's flathead info - Pennsylvania Fish and Boat Commission

Pylodictis olivaris (Global Invasive Species Database)

US Fish and Wildlife Service Ecological Risk Screening Summary for Pylodictis olivaris

Author: Fuller, P., M. Neilson, and R. Sturtevant

Peer Review Date: 4/1/2016

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.