The Neosho madtom is an endangered species in Missouri. It is our smallest catfish. It lives under rocks in riffles or runs in the clear waters of the Spring River in Jasper County.
Madtoms, as a group, are small, secretive catfishes that most people never see. The key identifier for madtoms has to do with the adipose fin (the small, fleshy fin that is present on the midline of the back just ahead of the tail fin). In madtoms, the adipose fin forms a low, keel-like ridge without a free, flaplike lobe along the trailing edge. The adipose may be connected to the tail fin, or it may have (at most) a slight notch in between. (In our other catfishes, the adipose fin forms a free, flaplike lobe, widely separate from the tail fin.)
The Neosho madtom can be distinguished by the following characters:
- The upper jaw projects well below lower jaw.
- Body has distinct blotches or bars (not uniformly colored).
- The dark patch at the base of the adipose fin extends only into the basal half of the fin.
- There is a dark, crescent-shaped bar across the middle of the tail fin.
- Small, sawlike teeth are poorly developed on the front margin of the pectoral fin spine; spines on back margin of spine are well-developed.
- The head length (from tip of snout to outer edge of gill covers) goes fewer than 3.5 times into the standard length (from tip of snout to base of tail fin).
Coloration is similar to the brindled madtom: the back and sides are yellowish brown with dusky mottlings, and the belly is pale yellowish white. The back with 4 dark crossbars. The fins are marked by prominent dark bands and blotches. In the Neosho madtom, however, the dark markings are more brownish instead of blackish, and the dark bars and blotches are less sharply defined.
Most madtoms possess a mild venom that is associated with the pectoral and dorsal spines. When introduced into a puncture wound produced by the spine, the venom causes a painful reaction. The spines are often erected and locked in place when the madtom is alarmed, increasing the chance of a puncture. The venom is not considered dangerous to people, and the chances of being “spined” are not great if the possibility is kept in mind when handling a madtom. If you’ve been jabbed by a madtom spine and think you’re having a severe reaction, seek medical attention.
Similar species: The Neosho madtom is most likely to be confused with the brindled and mountain madtoms. Those species differ by the following:
- The brindled madtom (N. miurus) has the dark color at the base of the adipose fin extending upward to near the fin margin (not limited to just the basal half of the fin). Also, the brindled madtom often has a narrow dark line, shaped like a question mark, at the base of the tail fin (the Neosho madtom never has that mark).
- The mountain madtom (N. eleutherus) does not have a dark, crescent-shaped bar across the middle of the tail fin. Also, the mountain madtom has small, well-developed sawlike teeth on the front margin of the pectoral fin spine (on the Neosho, they are poorly developed). Additionally, the mountain madtom is rare and only occurs in the southeast quarter of the state, not in the southwest.
There are about 30 species of madtoms (in the genus Noturus), and all occur in the central and eastern United States and nearby parts of Canada. In Missouri, 10 species of madtoms have been recorded. It can be difficult to separate the different species of madtoms using the traditional methods of fish ID (counting fin rays, for instance, or comparing ratios of body-part measurements). Noting differences in pigmentation (such as dark bars or patches) can help, but such coloration often varies by particular locality and habitat (such as amount of vegetation, turbidity, or different substrates). Color can also vary by a fish’s health, mood, breeding condition, sex, and individual genetics, and dead fish may show little coloration at all. Molecular (DNA) date is being used more and more as a way to separate the species; of course, it is not very useful in the field. Geography can be a good clue for species IDs, since different species may be restricted to certain stream systems and never occur in others.
Adult length: commonly 1¾–2¾ inches; maximum to about 3 inches. The smallest Missouri catfish.
While the entire distribution of the Neosho madtom comprises 250–300 stream miles of the Arkansas River basin, this species is peripheral in Missouri, inhabiting only 5–7 stream miles of the Spring River in our state.
Habitat and Conservation
You are unlikely to come across the Neosho madtom. It has a very limited distribution in Missouri. In our state, it has been collected only a few times from the Spring River just upstream from the Kansas-Missouri border.
Inhabits medium-sized to moderately large streams with moderate gradients, permanent flow, and fairly clear water. Adults are found on riffles, where loosely packed gravel provides crevices in which they hide. Young, and occasionally adults, live in quieter waters along the margins of rifles or downstream in the deeper, slower water of pools.
During daylight hours, the Neosho madtom buries itself in gravel substrate, emerging at night to forage.
This species is vulnerable to drought, pollution, and habitat changes due to reservoir construction, agricultural runoff, mining, and more.
Neosho madtoms hide during the day and come out at night to search for aquatic insects including the larvae of caddisflies, mayflies, flies, and midges. They feed most actively within three hours after sunset.
Endangered (state); Threatened (federal). A Species of Conservation Concern. This survival of this species is jeopardized by reservoir construction, gravel dredging, dewatering for municipal and agricultural purposes, and deteriorating water quality due to zinc-lead mining, agricultural runoff, and increased urbanization and industrialization.
It is not known if this species was ever more abundant in Missouri than it is now. However, it has suffered a decrease of its range and abundance in Oklahoma and Kansas. It has been extirpated from much of its former range in Oklahoma and northwestern Arkansas. All these states bear responsibility for conserving this species.
Little is known about the reproductive biology of this species. Apparently spawning occurs in June and July, which coincides with the period of peak streamflow in the river systems where this madtom lives. Spawning behavior is probably similar to that of similar madtoms, with nests being excavated by males under rocks or other protected places. After the eggs are laid, they are guarded by one or both parents. Some madtoms also guard newly hatched fish. Large numbers of young madtoms have been observed in the quiet water below riffles, suggesting that young-of-the-year fish probably drift downstream to develop. The maximum life span is probably 2 or 3 years.
Although it apparently has never been very abundant in the waters of our state, the Neosho madtom represents a precious, unique, and irreplaceable component of our Ozark waterways. Missouri, Kansas, and Oklahoma are the custodians for this little catfish.
This fish requires gravel riffles and swift currents, so construction of dams and reservoirs has destroyed much of this fish’s habitat. Cold water flowing downstream of the Tenkiller Dam killed all the populations of Neosho madtoms in the Illinois River in Oklahoma. Gravel dredging, pollution from cattle feedlots, and contaminants from urban and agricultural runoff are more human-caused threats for this fish’s survival. In drought years, people draw more water from reservoirs, leaving less water to flow downstream, drying up the rivers where these madtoms live.
Although most of Missouri’s species of madtoms may be collected and kept as aquarium fish (if you have a valid Missouri fishing permit; see the Wildlife Code of Missouri for details), you cannot collect or possess endangered or threatened species, including the Neosho madtom and mountain madtom.
The species name, placidus, means “mild,” “quiet,” or “gentle.” It seems a fitting name for this secretive, nocturnal, tiny catfish.
This small catfish controls populations of aquatic insects as well as flying insects, since many flying insects begin life as aquatic larvae.
Larger animals, including fish, mammals, and birds, prey on madtoms. Its secretive, nocturnal habit, camouflage color pattern, and stout, sawtoothed, venomous spines remind us that there are many animals that seek out this small catfish.
Healthy ecosystems provide fresh water, fertile soil, pollination, food, and medicine. Healthy ecosystems function best when all their components — the many species that live in them — are in place. When species are removed from the system, from extirpation or extinction, the system is weakened. The loss of a single species might not be disastrous, but the likelihood of problems increases as diversity decreases.
Non-point-source pollution is an important concept to understand. It’s easy to see how dumping a pollutant right into a stream can degrade water quality, but it’s a little harder to grasp how oil, detergent, salt, fertilizer, or pesticide applied to land that seems far from a stream is ultimately washed into our waterways. It’s also harder to see how construction or other soil disturbance on “dry land” can lead to siltation in nearby streams. Maintaining adequate buffer strips of vegetation along waterways is one way to help. Fortunately, people can learn these principles and take care to prevent our streams from being degraded.