Pygmy Madtom

views updated

Pygmy Madtom

Noturus stanauli

ListedApril 25, 1993
FamilyIctaluridae (Catfish)
DescriptionSmallest member of the catfish family; an unusually long adipose fin.
HabitatModerate to large rivers on shallow pea-size gravel shoals with moderate to strong current.
ThreatsSiltation and other pollution from poor land use practices, coal mining and waste discharge.


The madtoms are the smallest members of the catfish family. Madtoms can be distinguished by their small size and an unusually long adipose fin and round tail fin.

The Noturus stanauli (pygmy madtom) is the smallest of the known madtoms, growing to a maximum length of 1.5 in (3.8 cm). Its head is flat and is a dark brownish gray, except for the unpigmented areas around the tip of the snout and nares. It has a very distinctive pigmentation pattern, dark brown or black above the midline of the body and pale yellow or white below. Also, most or all of its fins are unpigmented, It has eight soft pectoral fin rays and 14-16 anal rays. The pectoral spines have strong recurred posterior serrae and well-developed anterior serrae.


Much of the species' life history is unknown However, much can be inferred from comparisons with closely related species, According to most recent phylogenies, the pygmy madtom's closest relatives are members of a group including the least madtom (Noturus hildebrandi) and the smoky madtom (Noturus baileyi).

The average life span of most madtoms is two or three years. However, members of the subgenus Rabida, of which the pygmy madtom is a member, are the shortest-lived madtoms, living only one to two years.

Pygmy madtom reproductive behavior is probably similar to that of closely related madtom species. Related madtoms nest in cavities beneath slabrocks and at times use other cover objects, such as cans and bottles. As native mussels are abundant in pygmy madtom habitat, it is possible that this species might use empty mussel shells for nesting cover. Reproduction likely occurs from spring to early summer; smoky madtom and least madtom reproduction occurs between late May and mid-July. Males guard eggs and young within their territories for several weeks, until the young are actively feeding. Other riffle-dwelling madtom species have been observed nesting in shallow heads or foots of pools, including the closely related smoky madtom and least madtom.

Madtoms almost exclusively prey on aquatic insect larvae. Most authors have suggested that they are primarily opportunistic feeders and take prey items in proportion to their abundance.

These fish possess a dangerous venomous pectoral spine with which they will not hesitate to inflict a wound in self-defense.


This species is found in moderate to large rivers on shallow pea-size gravel shoals with moderate to strong current. Although there are no observations of seasonal habitat shifts, the closely related smoky madtom is known to switch from riffles in summer and fall to overwinter in shallow pools. Many individuals are also found in the flowing portions of pools during the reproductive season.

This species' distribution overlaps the Oak-Hickory Ecosystem and Nashville Basin. The elevation is about 660 ft (200 m). Most of the outer part of the Basin is deeply dissected and consists of steep slopes between narrow rolling ridgetops and narrow valleys. The inner part of the Basin is predominantly undulating and rolling. The average annual precipitation is about 35-45 in (89-114 cm). The soils of this ecosystem are varied, have a thermic temperature regime, an udic moisture regime and a clay subsoil.


The fish fauna of the Tennessee River valley has been extensively surveyed; however, the pygmy madtom, which was likely once more widespread in the Tennessee River system, has been collected from only two short river reaches separated by about 600 river miles (965 river km). It has been taken from the Duck River, Humphreys and Hickman Counties, Tennessee, and from the Clinch River, Hancock County.


Generally this species of the pygmy madtom is threatened by water quality degradation as a result of siltation and other pollution from poor land use practices, coal mining and waste discharge.

The Tennessee and Cumberland Rivers are renowned as two of the most severely altered river-ine systems due to many anthropogenic activities. Most of the main stem of both rivers and many tributaries are impounded. In addition, there has been a loss of the riverine habitat and impoundments usually alter downstream aquatic habitats.

Siltation and toxic runoff have been the result of coal mining activities which unavoidably have adversely affected many reaches. Runoff from urban areas has also degraded water and substrate quality. The aquatic faunal diversity has declined due to this habitat destruction.

Because the two known populations are isolated from each other by impoundments, recolonization of any extirpated population is not be possible without human intervention. The absence of natural gene flow among populations of these fishes leaves the long-term genetic viability of these isolated populations in question. Additionally, several madtom species have, for unexplained reasons, been extirpated from portions of their range. In addition to visible habitat degradation, a variety of complex organic chemicals that may occur only in trace amounts have been added to the waters. Many madtoms are apparently restricted to only the best remaining riverine systems, suggesting that their specialized reproductive habits are impaired by contaminated water.

Due to the limited distribution of this species, a stochastic event such as an accidental toxic chemical spill could cause extirpation. As the populations are separated by impoundments natural recolonization of an extirpated population would be virtually impossible.

The pygmy madtom is not generally protected from threats other than take without a State permit.

Future activities which could impact this species are the issuance of permits for hydroelectric facility construction and operation, coal mining, reservoir construction, stream alterations, wastewater facility development, pesticide registration and road and bridge construction.

Conservation and Recovery

The U.S. Fish and Wildlife Service published a Recover Plan for the pygmy madtom in 1994. This endangered fish only survives in one short reach of a stream in the Tennessee River drainage: the Clinch River (it is probably recently extirpated from the Duck River). The objective of the recovery plan is to search for additional surviving populations, and to ensure the protection of the habitat of the known one. The plan also has criteria for enhancing the known habitat, monitoring the populations of the pygmy madtom, and conducting research into its biology and habitat needs, including methods of beneficial management. Crucial to the survival of the pygmy madtom is the improvement of its habitat, especially through better land-use practices that would reduce erosion and stabilize streambanks. It is also essential to take actions to prevent any potential spills of toxic chemicals into the Clinch River, as such an occur-rence could cause the extinction of the pygmy madtom. The rare fish should be bred in captivity, to provide stock for the establishment of one or more additional wild populations in suitable habitat.


U. S. Fish and Wildlife Service
Asheville Ecological Services Field Office
160 Zillicoa Street
Asheville, North Carolina 28801-1082
Telephone: (828) 258-3939

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345


U.S. Fish and Wildlife Service. 27 April 1993. "Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for the Duskytail Darter, Palezone Shiner and Pygmy Madtom." Federal Register

U.S. Fish and Wildlife Service. 1994. "Pygmy Madtom Recovery Plan." Atlanta, GA.