Endemic Madtoms

Two miniature catfishes are endemic to Arkansas—that is, they occur only in Arkansas and nowhere else on Earth. Both of these endemic fishes, the Ouachita madtom (Noturus lachneri) and the Caddo madtom (Noturus taylori), are taxonomically placed in the genus Noturus, the madtoms, which are contained within the catfish family Ictaluridae.

Noturus lachneri was originally described by William Ralph Taylor in 1969 from the type locality of the Middle Fork of Saline River at State Highway 7, 11.2 miles (18.1 kilometers) north of Mountain Valley in Garland County. It was believed to be confined to the upper Saline River drainage until a Northeastern Louisiana University graduate student discovered it in a small tributary of the main Ouachita River just below Remmel Dam in Hot Spring County in 1975. In the twenty-first century, it is common in tributaries of the Ouachita River near Hot Springs (Garland County). The Ouachita madtom lives in small to moderate-sized swift, clear streams with gravel substrates. It tends to inhabit the quieter backwater sections of the streams over gravel and cobblestone-sized rocks. Using electrofishing techniques, researchers have found high densities for this madtom averaging 95/100 m² (range 17 to 204/100 m²).

Characteristically, the Ouachita madtom is a slender, grayish-brown catfish with a white belly; a short, depressed head; terminal mouth; and jaws that are about equal in length. It has only a single internasal pore and ten preoperculomandibular pores on its head region. Small eyes are situated on the head, and it has a dorsal fin with a single spine and six soft rays. Anal fin rays usually number sixteen to eighteen, pelvic rays are eight to nine, and typically there are eight soft pectoral rays. Importantly, the pectoral spine is nearly straight and has no serrations on the front or back of the spine. The short adipose fin is described as adnate (without a free posterior flap) and is connected to the caudal fin. Adults of this madtom species range in size from about one to four inches.

The Ouachita madtom is not highly selective in food preference and eats a large variety of aquatic insect larvae as well as decapods, isopods, copepods, and gastropods. Feeding generally begins twenty to ninety minutes after sunset.

Spawning season of the Ouachita madtom begins in early summer and is completed by late summer. Like many other catfishes, N. lachneri is a nest builder and constructs its nests in shallow water above riffles and beneath flat rocks. After spawning is complete, the male guards the nest, which generally contains an average of thirty embryos. Nests with breeding males have been found from June to July at water temperatures of 17°C to 27°C. Fecundities of breeding females range from six to sixty-nine oocytes. Reproductive females have been estimated to be two years old, while longevity has been reported to be just over two years. The Ouachita madtom has been reported to harbor trematodes (Plagioporus sp.), unidentified tapeworm cysticerci, and larval Spiroxys sp. nematodes from Gulpha Creek near Hot Springs in Garland County.

The Ouachita Madtom has been considered “threatened” as a state species previously due to small population size, along with continued threats to its continued existence such as gravel removal, pollution, and possible impoundment. NatureServe ranks N. lachneri as imperiled (S2) in the state, and the Arkansas Game and Fish Commission lists this madtom as a Species of Greatest Conservation Need.

The second state endemic catfish species is Noturus taylori, which was originally described by Neil H. Douglas from specimens collected at the type locality of the South Fork of the Caddo River one mile (1.6 km) southeast of Hopper (Montgomery County) and named after William Ralph Taylor, the Smithsonian Institution expert on madtoms. Currently, the known distribution of the Caddo madtom includes the Caddo, upper Ouachita, and Little Missouri rivers of the Ouachita River drainage in the state. Two alternative hypotheses have been proposed to account for the present distribution of the Caddo madtom, and, by extension, the dynamics of the individual movement among localities. Recent dispersal could account for the distribution because no morphological divergence has been observed in this species, even among specimens from the most geographically distant localities. If this hypothesis is correct, then recent habitat fragmentation by dams might account for the high levels of genetic isolation observed in the Caddo madtom. Alternatively, localities among rivers might have been isolated for a long time. In this case, higher order rivers, such as the area of the confluence of the Caddo and Ouachita rivers, might have posed a barrier to gene flow for Caddo madtoms even before the construction of dams and impoundments on these rivers.

Typically, the Caddo madtom lives in shallow, gravel-bottomed pools of clear upland streams in the Ouachita Mountains. This madtom tends to inhabit areas below gravel riffles where it lives beneath large gravel, under rocks, and in the interstitial areas of rubble.

The Caddo madtom is a small, mottled catfish with black saddles covering a yellowish to white body and a whitish belly. A black blotch adorns the distal end of the fin, and the adnate adipose fin possesses a dark submarginal blotch. Anal rays usually number thirteen to sixteen, while pectoral rays are typically eight. There is usually only one internasal pore, although occasionally there may be two pores, while preoperculomandibular pores typically number eleven. The pectoral fin has small but well-developed anterior projections (serrae) present. The largest known Caddo Madtom specimen is just under three inches (7.5 centimeters).

Very few parasites have been reported from N. taylori. A trematode (Clinostomum marginatum), unidentified tapeworm cysticerci, and larval Spiroxys sp. nematodes have been reported from N. taylori from the Caddo River in Montgomery County.

Regarding its conservation status, some argue that this endemic catfish should be considered threatened in Arkansas due to loss of habitat in its rather small geographic range. NatureServe ranks N. taylori as critically imperiled (S1) in the state and the Arkansas Game and Fish Commission lists this madtom as a Species of Greatest Conservation Need. Because N. taylori is a headwater specialist, it is quite vulnerable to local extirpation. A genetic study of this madtom found that, at the within-drainage scale, fragmentation by natural or human activities such as the building of reservoirs possibly affects individual movement and recolonization probabilities, thereby resulting in genetic divergence of populations.

For additional information:
“Arkansas Endangered, Threatened, Regulated, and Species of Greatest Conservation Need.” Arkansas Game and Fish Commission. 2016.

Buchanan, Thomas M. “Small Fish Species of Arkansas Reservoirs.” Journal of the Arkansas Academy of Science 59 (2005): 26–42. Online at http://scholarworks.uark.edu/cgi/viewcontent.cgi?article=1531&context=jaas (accessed August 27, 2018).

Douglas, Neil H. “Noturus taylori, a New Species of Madtom (Pisces: Ictaluridae) from the Caddo River, Southwest Arkansas.” Copeia 1972 (1972): 785–789.

Fiorillo, R. A., R. B. Thomas, M. L. Warren, and Christopher M. Taylor. “Structure of the Helminth Assemblage of an Endemic Madtom Catfish (Noturus lachneri).” Southwestern Naturalist 44 (1999): 522–526.

Gagen, Charles J., Robert W. Standage, and J. N. Stoeckel. “Ouachita Madtom (Noturus lachneri) Metapopulation Dynamics in Intermittent Ouachita Mountain Streams.” Copeia 1998 (1998): 874–882.

McAllister, Chris T., Charles R. Bursey, Henry W. Robison, David A. Neely, Matthew B. Connior, and Michael A. Barger. “Miscellaneous Fish Helminth Parasite (Trematoda, Cestoidea, Nematoda, Acanthocephala) Records from Arkansas.” Journal of the Arkansas Academy of Science 68 (2014): 78–86. Online at http://scholarworks.uark.edu/cgi/viewcontent.cgi?article=1226&context=jaas (accessed August 27, 2018).

Patton, Tim M., and M. L. Zornes. “An Analysis of Stomach Contents of the Ouachita Madtom (Noturus lachneri) in Three Streams of the Upper Saline River Drainage, Arkansas.” Proceedings of the Arkansas Academy of Science 45 (1991): 78–80. Online at http://scholarworks.uark.edu/cgi/viewcontent.cgi?article=2131&context=jaas (accessed August 27, 2018).

Raymond, Larry R. “Fishes of the Hill Province Section of the Ouachita River, from Remmel Dam to the Arkansas-Louisiana Line.” MS thesis, Northeast Louisiana University, 1975.

Robison, Henry W. “Noturus lachneri Taylor, Ouachita Madtom.” In Atlas of North American Freshwater Fishes, edited by D. S. Lee et al. Raleigh: North Carolina State Museum of Natural History, 1980.

———. “Noturus taylori Douglas, Caddo Madtom.” In Atlas of North American Freshwater Fishes, edited by D. S. Lee et al. Raleigh: North Carolina State Museum of Natural History, 1980.

Robison, Henry W., and George L. Harp. “Distribution, Habitat, and Food of the Ouachita Madtom (Noturus lachneri Ictaluridae), a Ouachita River Endemic.” Copeia 1985 (1985): 216–220.

Robison, Henry W., and John L. Harris. “Notes on Habitat and Zoogeography of Noturus taylori (Pisces: Ictaluridae).” Copeia 1978 (1978): 548–550

Robison, Henry W. and Kenneth L. Smith. “The Endemic Flora and Fauna of Arkansas.” Proceedings of the Arkansas Academy of Science 36 (1982): 50–54. Online at http://scholarworks.uark.edu/cgi/viewcontent.cgi?article=2572&context=jaas (accessed August 27, 2018).

Robison, Henry W., and Thomas M. Buchanan. Fishes of Arkansas. 2nd ed. Fayetteville: University of Arkansas Press, 2020.

Stoeckel, J. N., Charles J. Gagen, and Robert W. Standage. “Feeding and Reproductive Biology of the Ouachita Madtom.” In Conservation, Ecology, and Management of Catfish: The Second International Symposium, edited by P. H. Michaletz and V. H. Travnichek. Bethesda, MD: American Fisheries Society, 2011.

Taylor, William R. “Revision of the Catfish Genus Noturus Rafinesque, with an Analysis of Higher Groups in the Ictaluridae.” Bulletin of the United States National Museum 282 (1969): 1–315.

Tumlison, Renn, and J. O. Hardage. “Growth and Reproduction in the Ouachita Madtom (Noturus lachneri) at the Periphery of its Distribution.” Journal of the Arkansas Academy of Science 68 (2014): 110–116. Online at http://scholarworks.uark.edu/cgi/viewcontent.cgi?article=1231&context=jaas (accessed August 27, 2018).

Tumlison, Renn, and Creed Tumlison. “A Survey of the Fishes in Streams Draining the Jack Mountain Area, Hot Spring and Garland Counties, Arkansas, with Notes on the Ouachita Madtom (Noturus lachneri).” Proceedings of the Arkansas Academy of Science 50 (1996): 154–159 Online at. http://scholarworks.uark.edu/cgi/viewcontent.cgi?article=1869&context=jaas (accessed August 27, 2018).

Turner, T. T., and Henry W. Robison. “Genetic Diversity of the Caddo Madtom, Noturus taylori, with Comments on Factors that Promote Genetic Divergence in Fishes Endemic to the Ouachita Highlands.” Southwestern Naturalist 51 (2006): 338–345.

Warren, M. L., Jr., and Brooks M. Burr. “Status of the Freshwater Fishes of the United States: Overview of an Imperiled Fauna.” Fisheries 19 (1994): 6–18.

Henry W. Robison
Sherwood, Arkansas

Chris T. McAllister
Eastern Oklahoma State College