Madtoms are members of the catfish (see) family, Ictaluri-dae, often referred to as bullhead catfish. Although the larger members of the catfish family have gained notoriety as sportfish, commercial fish, or food fish, the secretive and diminutive madtom escapes public attention.
These are little-known fish with interesting lifestyles. Madtoms are important links in the food webs of many streams, making it possible for large predators such as bass, wading birds, and water snakes to benefit from the stream's vast energy, represented by larval insect production. They are also a unique natural resource to North America's small streams and are endemic to the continent north of Mexico. The 40 species belonging to the family Ictaluridae occur naturally in the United States and Canada, and 27 are madtoms.
Like other members of the Ictaluridae family, madtoms possess stinging venom in their dorsal and pectoral spines. The venom originates from cells of the skin sheath over the pectoral fin. The toxicity of the venom varies but approximates that of a bee sting, although every person reacts differently to being stung.
Identification/Size. The madtom is recognized by its unique adipose fin. A non-madtom catfish has a fleshy fin protruding from its back, just ahead of the caudal fin. The adipose fin of a madtom is continuous with the caudal fin.
Madtoms belong to the genus Noturus, which is divided into three subgenera, Noturus, Schilbeodes, and Rabida, each with its own distinct appearance. The Schilbeodes are dull colored, generally brown or yellow brown. Those in Rabida have colorful markings with many bands and saddlelike pigmentation. There is only one species in the subgenus Noturus, the stonecat (Noturus flavus). The stonecat possesses the plain appearance of the Schilbeodes; however, no other madtoms match this species in size.
Habitat. Most anglers are probably unfamiliar with madtoms because they tend to be nocturnal, hiding under rocks, logs, and undercut banks during the day. Also, their body markings and color patterns (or lack of, depending on their preferred habitats) help camouflage them from the peering eyes of birds, water snakes, and anglers. Most madtoms prefer the cool, clear water of smaller streams, but some species are adapted to living in lakes, large streams, or muddy rivers. Where aquatic vegetation and beaver dams exist, madtoms take full advantage of their numerous niches.
Most madtoms have strong habitat preferences and thus use unique habitats. The stonecat primarily inhabits small to large rivers with rubble or boulders and lakes with gravel bars. In contrast, the black madtom prefers vegetation over gravel or sand in the clear moving water of springs, creeks, and small rivers. The
Madtoms (continued) margined madtom prefers rocky riffles with fast-moving water in small and medium-size rivers. Different species are even known to prefer rocks of specific sizes for cover. Because madtoms are choosy about their homes, they often have problems dealing with the degradation of their preferred habitats.
Stonecats exceed 7 inches as adults and may reach 12 inches in some locations. Madtoms range from 2V2 inches to 6V2 inches.
Reproduction. Madtoms start spawning about mid-April and finish spawning in mid-July. As with most fish, the commencement of spawning and the length of the spawning season depend heavily on water temperature. Madtoms usually begin spawning after the water temperature has reached 64°F and stop spawning after the water temperature exceeds 81°F. During the spawning season, adults are sexually dimorphic, which means males look different from females.
Madtoms construct nests to rear their young and provide post-spawning protection. A nest consists of an area with a pebble or gravel substrate that has been cleared of silt and debris.
Most madtoms prefer to nest under rocks; however, the speckled madtom and others have been known to nest in discarded beverage cans or bottles.
Although madtoms are small fish, they have relatively fewer and larger eggs compared to species that do not exhibit parental care. Madtom eggs may be up to 0.2 inches in diameter; they are adhesive and stick to the substrate and each other. Generally, a short time after laying the eggs, the female leaves the nest and the parental duties to the male. Eggs hatch in 8 to 10 days, depending on water temperature. After approximately 21 days of parental care, the male parent will leave the young madtoms on their own.
Food. Madtoms are crepuscular feeders, which means they feed mostly at dusk and dawn. As insectivores, they primarily feed on a diet of midge larvae, mayfly larvae, caddisfly larvae, and crayfish. Most madtoms are not as picky about their food as about their housing and will eagerly devour any available prey. Madtoms generally consume smaller amounts of stonefly, beetle, black fly, dragonfly, alder fly, and fish fly larvae. An occasional small fish (such as lamprey larvae), a spider, or zooplankton have also been found in their stomachs. When placed together, large adult madtoms have consumed small juvenile madtoms of the same species.
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