Madtoms are members of the catﬁsh (see) family, Ictaluridae, 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/SizeThe 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.
Stonecats exceed 7 inches as adults and may reach 12 inches in some locations. Madtoms range from 21⁄2 inches to 6.5 inches.
ReproductionMadtoms 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.
FoodMadtoms 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.