About Noturus nocturnus Jordan & Gilbert, 1886
Noturus nocturnus, commonly known as the freckled madtom, is a species of freshwater madtom catfish found in the eastern United States. The freckled madtom is a benthic feeder that mostly eats invertebrates. It typically inhabits medium to large bodies of water, and lives most often in riffle areas with clear water and rocky bottoms. Its spawning season runs from spring to early summer, and spawning takes place in riffle areas. Individuals reach sexual maturation after two years. The freckled madtom is a freshwater species distributed across the eastern United States, and it is common across most of its range. Its range covers the Mississippi River basin and Gulf of Mexico tributaries in Alabama, Mississippi, Louisiana, and Texas. The species is also found in the lower Ohio River basin in Kentucky, Indiana, and Illinois. Additional areas where it occurs include Oklahoma, southeastern Iowa, central Kansas, Arkansas, Georgia, and western Tennessee. It occurs mostly between 41°N and 30°N latitude. This range has been documented since at least 1980; current distribution matches historical distribution, though small northward range extensions have occurred, possibly due to global warming. The species is not known to travel often, especially over long distances. The full distribution of the freckled madtom is not completely known, due to its small population sizes and tendency to be easily misidentified, often mistaken for bullheads or other catfish. The freckled madtom is an intolerant species that sometimes disappears after an ecological disturbance. It is a fluvial specialist, meaning it is specialized to live in its specific habitat of fast-moving riffle environments. Human litter may act as a potential disturbance to this species; young freckled madtoms and breeding adult males have often been found inside beverage cans and other human-created debris. Range expansion can be difficult to detect because of small population sizes in some areas, including central Oklahoma. However, freckled madtom distributions may have extended slightly as water quality has improved in some regions. In ecology, the freckled madtom inhabits fast-moving, permanently flowing medium to large streams that usually have rocky bottoms. It can sometimes also be found near undercut banks next to masses of sticks and roots. The freckled madtom is primarily an invertivore that feeds using ambush tactics in benthic regions, mostly at night. It notably consumes insect larvae, including mayfly, black fly, caddisfly, and midge larvae, and it also occasionally eats crustaceans. While it is mostly an invertivore, it has also been documented occasionally eating other fish. Evidence of freckled madtoms feeding on the smaller speckled madtom (N. leptacanthus) has been found in southern Mississippi. To help subdue its prey, this catfish has venom glands along the smooth spines of its pectoral and dorsal fins.
