Ohio River (Rafinesque 1818).
Etymology/Derivation of Scientific Name
Pylodictis, Greek, meaning “mud fish;” olivaris, Latin, meaning “olive-colored” (Pflieger 1997).
Pilodictus olivaris Hay 1881:514.
Leptops olivaris Hay 1883:74; Evermann 1899:306; Hildebrand and Towers 1928:121.
Pylodictus olivaris Cook 1959:140.
Maximum size: 1410 mm TL (Carlander 1969).
Life colors: Back and sides gray to brown with dark brown-black mottling that may extend ventrally onto belly. Undersides of head and body white to yellow. Nasal and maxillary barbells dark; chin barbells white to yellow. In large fish, chin barbels may be slightly dusky, never black. Adipose fin dusky or mottled, frequently having a light margin in small fish. Pelvic, pectoral, and dorsal fins densely covered with melanophores in the basal half to three-quarters of the fins, the remaining marginal areas unpigmented. Anal fin dusky, frequently having a black marginal band. Caudal fin dusky. Immature fish have a light-colored patch on the tip of the upper lobe of the tail, which seems to disappear when fish mature (Ross 2001).
Counts: 8-10 gill rakers; 6-7 dorsal rays; 16-17 (14-17) anal rays; 8-11 pectoral rays; 9 pelvic rays (Ross 2001).
Body shape: Slender, elongated; becoming moderately robust as adults (Ross 2001). Head depressed (Hubbs et al. 1991).
Mouth position: Terminal (Goldstein and Simon 1999). Lower jaw projects forward beyond the upper jaw (Ross 2001).
External morphology: Adipose fin free at tip, not joined to caudal fin (Hubbs et al 1991). Anal fin base quite short, length goes into SL 5.3-6.3 times. Small eyes (Ross 2001). Males have prominent posteriorly directed genital papilla with a small rounded urogenital opening at tip. Females have a recessed genital papilla with a larger urogenital opening that appears as a long slit. Urogenital opening of adult female becomes inflamed in late spring and summer (period of greatest spawning activity; Johnson 1950; Turner and Summerfelt 1971). Genital papilla of immature females invaginated and hardly discernable (Turner and Summerfelt 1971).
Internal morphology: Premaxillary band of teeth on upper jaw with a lateral backward extension on each side (Hubbs et al. 1991). Ratio of digestive tract (DT) to total length (TL): DT 1.0 TL (Goldstein and Simon 1999).
Distribution (Native and Introduced)
U.S. distribution: Ranges throughout the Mississippi, Ohio, and Missouri basins southward along the Gulf drainages to Mexico (Hubbs et al. 1991).
Texas distribution: Species occurs statewide (Hubbs et al. 1991). Warren et al. (2000) list the following drainage units for distribution of Pylodictis olivaris in the state: Red River (from the mouth upstream to and including the Kiamichi River), Sabine Lake (including minor coastal drainages west to Galveston Bay), Galveston Bay (including minor coastal drainages west to mouth of Brazos River), Brazos River, Colorado River, San Antonio Bay (including minor coastal drainages west of mouth of Colorado River to mouth of Nueces River), Nueces River.
Abundance/Conservation status (Federal, State, NGO)
Southern drainage populations are currently stable (Warren et al. 2000).
Macrohabitat: Characteristic of deep holes of medium and large-sized rivers (Glodek 1980). Large streams (Minkley and Deacon 1959).
Mesohabitat: Deep, quiet pools of main rivers, being found in tributary streams only in deep pools adjacent to the main stream (Cowley and Sublette 1987).Young-of-the-year live in rubble bottomed riffles until between 2 and 4 inches in length. At that size fish become more evenly distributed in the stream; some remain in riffles, but more move into pools, deeper riffles, and into almost all other habitats. This random distribution seems the rule in fish ranging from 4 to 12 inches in length. Individuals measuring 12 to 16 inches in length were associated with cover at intermediate depths in the stream, while larger individuals, more then 16 inches in length, almost invariably near more massive logs and drift usually in or near deep holes in the stream bed (Minkley and Deacon 1959).
Spawning season: In Texas, late June and July (Hubbs et al. 1953; Munger and Deacon 1959).
Spawning location: Nests constructed under logs or other concealing cover (Breder and Rosen 1966).
Spawning Behavior: Guarders; nest spawners; spleophils – hole nesters (Simon 1999). Nests constructed by both male and female. After chasing female from the nest, male remains to guard nest and care for eggs and young (Breder and Rosen 1966). Henderson (1965) reported that males in Texas hatchery pens behaved viciously while guarding eggs; male would “tear the female to pieces” when she attempted to enter the spawning jar which contained eggs; a number of females that had spawned were killed by the male, in spite of efforts to remove the female from the area as soon as possible.
Fecundity: Eggs are gelatinous, adhesive (Breder and Rosen 1966). In small hatchery-reared brood fish, spawns numbered from 3,000-5,000 eggs (Henderson 1965). In Kansas, Minckley and Deacon (1959) reported that females of 305-610 mm TL can produce from 6,900-11,300 eggs, averaging 2.8-3.2 mm diameter. Depending on size of females ranging from 1.05-11.66 kg, in an Oklahoma reservoir, 4,076 – 58,792 eggs were laid; ripe eggs averaged 3.7 mm diameter (Turner and Summerfelt 1971). Snow (1959) reported egg mass weighing slightly less than 1,089 g (2.4 lb) which contained about 15,000 eggs. Giudice (1965) reported hatching of eggs in 6-7 days at 23.9-27.8 degrees C; Snow (1959) reported hatching in 9 days at 24-25.9 degrees C, fry averaging 11 mm long.
Age/Size at maturation: In Texas reservoirs, individuals become sexually mature between ages 2 and 5 at a total length between 290 and 635mm (Munger et al. 1994).
Minckley and Deacon (1959) reported mature males at 3-4 years, and females at 4-5 years. Carlander (1969) reported males usually maturing at 3-5 years old, after exceeding 38 cm TL, while females mature at 4-6 years old, and in excess of 46 cm TL.
Migration: Sedentary (Funk 1957; Robinson 1977; Dames et al., 1989; Jackson 1999), with 1-3 'home sites' they return to after nighttime movements (Vokoun and Rabeni 2005).
Growth and Population Structure: Ross (2001) summarized large amount of age and growth data, noting that rates vary considerably among areas, and seem to be higher if individuals make early transition to a fish diet. In general, fish reach 51-353 mm TL at the end of one year, and 168-484 mm, 238-649 mm, 374-758 mm, 497-843 mm, 581-951 mm, 795-1054 mm, 824-1099 mm, and 1100 mm TL at ages 2-14 respectively.
Longevity: Lifespan can exceed 19 years (Carlander 1969).
Food habits: First and second level trophic classifications are invertivore/carnivore, and benthic and drift/whole body, respectively; feeding behavior: passive predator. Main food items of juveniles are microcrustaceans and insect larvae; main food items of adults are crayfishes, clams, and particularly fishes including Carpiodes carpio, Notropis buchanani, N. lutrensis, N. stramineus, Semotilus atromaculatus, Ictalurus punctatus, Noturus nocturnus, Pylodictis olivaris, Lepomis megalotis, Percina phoxocephala, and Aplodinotus grunniens (Minckley and Deacon; Goldstein and Simon 1999; Jackson 1999). Primarily nocturnal feeders (a time when prey are more vulnerable to visual deception; Moyle 1976) that forage in a wide variety of habitats (Etnier and Starnes 1993), including area shallow enough to expose dorsal fin (Trautman 1957); most feed by lunging and seizing prey after lying motionless (Minkley and Deacom 1959). Trautman (1957) reported having seen large individuals lying motionless on the bottom with an open mouth; personal communications from local Ohio fisherman conveyed reports of cover-seeking prey swimming into the open mouths of fishes; further, large numbers of hiding species such as rock bass (Ambloplites rupestris), spotted blackbass (Micropterus puntulatus), and small catfishes (Ictaluridae) have been found in stomachs of large flatheads, lending credence to these statements.
Phylogeny and morphologically similar fishes
Monotypic genus (Glodek 1980) Pylodictis apparently unchanged since mid-Miocene, forming the sister taxon to the blind, subterranean genus Satan; Pylodictus and Satan are sister group to a clade containing Noturus (Lundberg 1992; Ross 2001). Unlikely to be confused with other catfishes, as it differs from the channel (Ictalurus punctatus) and blue (Ictalurus furcatus) catfishes in having a rounded caudal fin (versus a forked), and from the bullheads (Ameiurus) in having a greatly flattened head, posterior extensions of the premaxillary tooth patch, and a projecting lower jaw (Ross 2001). Etnier and Starnes (1993) noted juveniles might be mistaken for one of the madtom species (Noturus); however the free posterior end of adipose fin of Pylodictis is apparent even in small sizes. Pylodictis olivaris reported to hybridize with the channel catfish (Ictalurus punctatus; Trautman 1957).
In Kansas populations, the cestode, Marsipometra, was commonly found in the duodenum and nematodes occurred occasionally in the hindgut (Minkley and Deacon 1959). Becker (1983) noted that Pylodictis olivaris is host to the glochidia of a number of freshwater mussels, including Amblema plicata, Megalonaias gigantean, Quadrula nodulata, Q. pustulosa, Q. quadrina, and Elliptio dilatata.
Commercial or Environmental Importance
Rapid dispersal and population growth rates of introduced flathead catfish, along with their obligate carnivorous food habits, have caused concern among ichthyologists and management agencies (Brown et al. 2005). United States Fish and Wildlife Service had placed the flathead catfish as its highest priority among invasive animal species in the southeastern United States (Memorandum dated 3 November 1999; Brown et al. 2005). Species can attain sizes greater then 1000 mm TL, and weigh more than 50 kg, and is regarded by many anglers to be a big game fish (Carroll and Hall 1964; Jackson 1999). Overall U.S. angling record of 44.5 kg (98 lb) was caught in Texas in 1986 (Ross 2001). Henderson (1965) noted that fingerling mortality was very high in ponds where large numbers of crayfish were present.
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