Catfishes, members of the family Ictaluridae, are easily recognized by conspicuous barbels around their mouths and scaleless bodies. The pectoral and dorsal fins are equipped with spines that can inflict wounds causing considerable discomfort, depending on the particular species. The flathead catfish is the only member of the genus Pylodictis. This species can be distinguished by a white blotch on the dorsal lobe of the caudal fin (except in large adults), an adipose fin which is fused to the body along its entire length, and an anal fin with less than 17 rays. The fish are typically yellowish with brown mottling. The species gets its scientific name from its flattened head, protruding lower jaw, and coloration. Adults commonly reach 115 cm (45 in) long and generally weigh up to 23 kg (50 lbs). The current South Carolina record weighed 33.5 kg (74 lbs).
Habitat and Biology
Flathead catfish are typically found in freshwater rivers and reservoirs, but they can also inhabit brackish water. They are benthic inhabitants and utilize their barbels to locate food in the substrate. They are very secretive and spend the daylight hours associated with some type of aquatic cover. Foraging occurs at night, often in areas so shallow that their dorsal fins are exposed. Juveniles feed on immature insect larvae in riffle areas, and adults primarily target fish and crayfish. Adults are generally a solitary species, except during the spawning season. They prefer deep pools with heavy submerged cover. At night they move to shallow areas to feed. Young fish can be found in shallower areas around roots or riprap.
This species spawns in June or July. The eggs are laid in a large nest fanned out on the bottom in a natural cavity or near a large, submerged structure. An egg mass of up to 100,000 eggs can be produced by a large female. The eggs are agitated continuously by the male parent, which helps to provide oxygen and flush away silt from the nest. After the eggs hatch, the fry remain in a compact school around the nest for several days, guarded by the male fish. They soon disperse and begin a solitary existence. The fry first feed on insect larvae, but as they grow, fish and crayfish become more important in the diet. Large adults are almost completely piscivorous. The species reaches sexual maturity at 4 or 5 years of age. Trophy size can be reached in about 10 years.
Flathead catfish are not native to the ACE Basin but are originally from the Mississippi River drainage. They were first introduced into Lake Thurmond and Lake Marion in the early 1960s. North Carolina stocked the species in the Pee Dee drainage, and they have migrated from there downstream into South Carolina. Because of unauthorized releases, they are now found in several coastal rivers of the state, including the Edisto River in the ACE Basin. In the Edisto River, they have been found throughout the main branch and are beginning to move into the north and south forks.
In the Edisto River system, flathead catfish have had profound effects on native catfish and sunfish species. All three of the once plentiful bullhead catfish species are now rare. Redbreast sunfish populations appear to have also been drastically reduced since the introduction of flathead catfish into the system. Because flathead catfish have been found in estuarine reaches of the river, it is speculated that they may also impact some marine and amphidromous species as well. Most notable would be their potential impacts on shortnose sturgeon, which use the estuarine reaches of the river as feeding grounds during the winter. Currently, the Freshwater Fisheries Section of the South Carolina Department of Natural Resources is gathering data on life history information, and investigating the impacts of this species on the ecology of the Edisto River.
Allen, D. 1998. pers. comm. South Carolina Department of Natural Resources, Freshwater Fisheries Division, Barnwell, SC.
Allen, D.E. and C.S. Thomason. 1993. Survey and inventory of fisheries resources in the Combahee River. Study Completion Report F-32. SC Wildlife and Marine Resources Department, Columbia, SC.
Thomason, C.S., D.E. Allen, and J.S. Crane. 1993. A fisheries study of the Edisto River, SC. Wildlife and Marine Resource Department, Study Completion Report, Federal Aid Projects F-32 and F-30.