Noturus, the madtoms, is a genus of small North American catfish in the family Ictaluridae, the same family as the channel and bullhead catfishes, restricted to the United States and Canada. Madtoms are secretive, mostly nocturnal fish that shelter by day under rocks, logs, or leaf packs in streams and small rivers, emerging at night to forage for aquatic insects and other invertebrates. A defining feature of the genus is a venom gland at the base of the pectoral (and sometimes dorsal) spines, which delivers a sharp, bee-sting-like pain if a fish is mishandled -- mild for a human but a genuine defense against predators. The atlas covers 20 species with adult sizes from about 2–10 in, most species sitting well toward the smaller end of that range.
Noturus is a genus of far more scientific and conservation interest than aquarium-trade relevance; madtoms are almost never sold commercially and are kept mainly by native-fish enthusiasts rather than the mainstream hobby. Many species have naturally small ranges, often confined to a single river drainage, which leaves them acutely exposed to damming, siltation, and pollution -- a vulnerability reflected clearly in the atlas's tally, with a Critically Endangered species, two Endangered species, and two more rated Vulnerable alongside the more secure majority. Species such as Noturus baileyi (Smoky madtom) and N. furiosus (Carolina madtom) are emblematic of this pattern: fish with restricted historic ranges now the subject of active conservation attention rather than the aquarium spotlight.