Burr, BM; Stoeckel, JN; ,
Of the 25 described species of Noturus, or madtoms, about two-thirds have adequate information available on their life histories, and this information is derived from 38 studies. Five species are listed as threatened or endangered by the U.S. Fish and Wildlife Service. Madtoms as a group are the smallest ictalurids, with nearly 70% of the species reaching less than 100 mm standard length (SL). Madtoms exhibit life history traits not unlike other members of the family Ictaluridae, including nocturnal life styles, relatively low annual fecundities, large embryo and hatchling sizes, cavity nesting, summer nesting seasons, extreme parental care, head-to-tail spawning positions, and benthic habitations. The constraint of being small probably accounts for many of the differences between madtoms and other ictalurids including a relatively short-life, a largely invertebrate diet, and a low lifetime fecundity. Most madtoms do not live beyond 3-4 years, although extremes include three annual species and another six species that live 5+ years. Diet includes mostly insects, some crustaceans, and occasionally crayfishes or fishes. Feeding activity is primarily nocturnal or crepuscular with peaks in feeding occurring at dawn and dusk. Mean annual absolute fecundity (ovarian) ranges from 24 and 30 oocytes per female in small (<60 mm SL) species to 378 in the stonecat Noturus flavus, the largest species. The largest species, stonecat, is more fecund than congeners in number of progeny per female, but mature females are larger and produce slightly fewer oocytes per gram body weight. Species on the lower end of the size continuum mature in their first year; whereas, the largest species mature later in life (2-4 years). All nests with egg clutches have been found in cavities beneath stones, logs and boards or in cans, bottles, and bivalve shells, and are guarded predominantly by males. Annual mean nest clutch production barely exceeds 100 embryos when clutch sizes across the 18 studied species are averaged. Longevity and maturation data indicate that both iteroparity and semelparity occur in madtoms. The flathead catfish Pylodictis olivaris is the epigean sister group to madtoms and the two genera share a number of reproductive traits (e.g., male parental care only) that differ from those observed in species of bullheads Ameirus. Madtoms are among the least fecund of North American freshwater fishes and their fertilized eggs are among the largest reported outside the Salmonidae. Aspects of natural history requiring further research include: 1) quantification of spawning behaviors, 2) nest construction and differential participation of the sexes, 3) social behaviors, 4) contribution of females in parental care, 5) number of clutches spawned per season by an individual female and number of lifetime clutches produced, 6) behavior and distribution of young after leaving the nest, 7) critical diurnal habitats, 8) movements or migrations, 9) nocturnal behaviors, 10) winter habitat occurrence, 11) interactions with other organisms, 12) nest fidelity in subsequent breeding seasons, 13) geographic and population variation in life history traits, and 14) potential phylogenetic constraints on life history traits.
Irwin, ER; Hubert, WA; Rabeni, CF; Schramm, HL; Coon, T;
