New Orleans (Lesueur 1840).
Etymology/Derivation of Scientific Name
Ictalurus, Greek, meaning “fish cat;” furcatus, Latin, meaning “forked,” in reference to the tail fin (Pflieger 1997).
Pimelodus furcatus Lesueur 1840:136.
Ictalurus furcatus Hildebrand and Towers 1928:119; Cook 1959:137.
Maximum size: 1194 mm TL (Glodek 1980).
Coloration: Back bluish grey; sides silvery grey (diffuse spotting apparent in some preserved specimens); abdomen grayish white (Sublette et al. 1990). Breeding male dark blue (Moyle 1976). Rio Grande River, Texas population reportedly differs from other blue catfish in that the juvenile and young are very speckled and many adults retain their spots (Wilcox 1960).
Counts: Anal fin rays 30-36 (Hubbs et al 1991); 6 dorsal rays; 8-10 pectoral rays; 8 pelvic rays; 14-21 gill rakers (Ross 2001).
Body shape: Moderately robust, elongate (Ross 2001); head rounded (Hubbs et al. 1991).
Mouth position: Subterminal (Goldstein and Simon 1999); lower jaw never protrudes beyond the upper jaw (Graham 1999).
External morphology: Caudal fin deeply forked; head rounded; adipose fin free at tip, not joined to caudal fin; eyes present (Hubbs et al 1991).Genital orifices of the male and female are distinct; in the male, papilla is more prominent with a circular opening; in the female, it is more recessed and the opening is slitlike (Moyle 1976).
Internal morphology: Premaxillary band of teeth on upper jaw without a lateral backward extension on each side (Hubbs et al 1991); swim bladder is restricted, forming two approximately equal chambers (Ross 2001).
Distribution (Native and Introduced)
U.S. distribution: Native to major rivers of Mississippi, Missouri, and Ohio basins of central and southern United States, south into Mexico and northern Guatemala; introduced to Rappahannock and James drainages, Virginia (Glodek 1980). Numbers in their native range have been greatly reduced due to alteration of riverine habitats, particularly on the periphery of their range (Graham 1999).
Texas distribution: Ranges in all except the northwestern part of the state (Hubbs et al. 1991). Warren et al. (2000) list the following drainage units for distribution of Ictalurus furcatus 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)
Populations in southern drainages are currently stable (Warren et al. 2000).
Macrohabitat: In Texas, blue catfish usually inhabit larger rivers and streams (Hubbs et al 1991).
Mesohabitat: Inhabits mostly swift chutes and pools of noticeable current, and silt-free sand, gravel and rubble substrates (Glodek 1980; Pflieger 1975, 1997). Normally found in open waters of large reservoirs and main channels, backwaters, and in flowing rivers with strong current where water is normally turbid (Burr and Warren 1986). Will enter brackish water with salinities up to 3.7 ppt; occasionally found in salinities of 11-15 ppt (Perry 1968; Christmas and Waller 1973).
Spawning season: Occurs in late spring and early summer at water temperatures of 21-25 degrees C (Sublette et al. 1990). In Louisiana, spawning in April and May (Jordan and Evermann 1916; Pflieger 1975); in Illinois, spawning occurs in June (Smith 1979).
Spawning location: Nest (cavity) constructed by the male, often in pools and backwaters (Sublette et al. 1990; Simon 1999).
Reproductive behavior: Guarders; nest spawners; speleophils – hole nesters (Simon 1999). Nesting habits are similar to those of channel catfish (Ictalurus punctatus; Pflieger 1975). Nest is constructed and cared for by the parents until the young hatch (Smith 1979).
Age/Size at maturation: In Louisiana, males are mature by 4th year at length of 490 mm TL; females at 5th year, at length of 590 mm TL (Perry and Carver 1973).
Migration: May undertake seasonal movements in response to changes in water temperature. In the lower Mississippi River, reported to move farther down river where water is warmest in winter, running upstream in summer (Jordan and Evermann 1916; Pflieger 1975).
Growth and Population structure: In Lake Texoma, Oklahoma, fish reach 5.7 inches at the end of 1st year, and averages 10, 13.8, 17.4, 21, 25.8, 30.3, 34.3, 40.4, 42.1 and 44 inches at the end of succeeding years (Jenkins 1956). Growth of Ictalurus furcatus in Lake Texoma is more rapid than that of channel catfish (I. punctatus), and almost the equivalent to that of the flathead catfish (Pylodictus olivaris; Pflieger 1975). In Sardis Reservoir in northern Mississippi, and in Kentucky Lake on the Tennessee River, blue catfish reached a TL of 88- 135 mm after one year, and TL of 166-198 mm, 251-266 mm, 297-330 mm, 356-392 mm, 429-456 mm, 510-513 mm, 582-614 mm, and 698 mm for years 2-9, respectively (Conder and Hoffarth 1965; Schultz 1967).
Longevity: At least 14 years (Kelley 1969); Ross (2001) and Smith (1979) note that life expectancy is likely over 20 years due to large sizes found.
Food habits: First and second level trophic classifications listed as invertivore/carnivore and benthic/whole body, respectively; main food items including an array of invertebrates, fishes, and occasionally frogs (Goldstein and Simon 1999). Food items widely varied, seemingly upon prey availability. Some populations feed primarily on fishes, especially small minnow; in coastal areas, mainly bay anchovies (Anchoa mitchilli), but consuming crustaceans (penaeid shrimp and small crabs) as well. Other populations feed more on invertebrates such as crayfishes, larval dragonflies, hellgrammites, chironomid larvae, and mayfly larvae (Brown and Dendy 1961; Darnell 1961; Lambou 1961). Three general feeding stages noted during growth: Fish smaller than 100 mm SL feed in the water column on zooplankton (including calanoid copepods and mysid shrimp, in coastal areas). Individuals from 100-240 mm SL feed on small bottom-inhabiting invertebrates including immature aquatic insects, amphipods, mud crabs (Rhithropanopeus), mollusks (such as rangia clams, mussels, gastropods), and organic detritus. At 240 mm SL and larger, fish feed on large, mobile organisms including shrimp, crabs and fishes (Darnell 1958; Minckley 1962; Perry 1969; Davis 1979). Davis (1979) reported increased feeding activity at night, especially between midnight and sunrise.
Phylogeny and morphologically similar fishes
Ictalurus furcatus is a member of the I. furcatus species group, which is the sister group to the I. punctatus clade (Lundberg 1992). I. furcatus most closely resembles the headwater catfish (I. lupus) and the channel catfish (I. punctatus) but differs by a smaller eye situated more anteriorly; a longer and straighter margin on the anal fin; a median keel-like crest anterior to the dorsal fin; a crest on the dorsal edge of the opercle; the sides lacking dark spots; and a higher number of anal rays (I. furcatus usually >32; I. puntatus usually 25-28; I. lupus usually <25; Sublette et al. 1990).
Commercial or Environmental Importance
Ictalurus furcatus considered recreationally valuable in the state of Texas, and is used to add diversity to fisheries (Graham 1999). Ictalurus furcatus, or its hybrid with the channel catfish (I. punctatus), has been reared commercially. However, the majority of commercial production of catfish in the United States is from Ictalurus punctatus (Stickney 1986; Sublette et al. 1990). Graham (1999) noted that the species lacks popularity with aquaculturists, but hybrids developed with channel catfish are frequently used in fee-fishing lakes because of their rapid growth and aggressive disposition. Related fossil ictalurid, Ictalurus lambda, known from Pliocene deposits of Kansas (Hubbs and Hibbard 1951).
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