Northern madtom
The northern madtom (Noturus stigmosus) is a freshwater fish. Ranges and habitat N. stigmosus can be found in the Ohio River valley stretching into distinct locations in Canada, where it is considered endangered. It is a fairly rare species with little data available because such small numbers are observed. The northern madtom prefers habitats with relatively swift currents along with sand, silt, or rocky substrates. The species begins spawning around 23 °C, which is sometime in early summer throughout its range. It is a cavity nester and builds its nests under large rocks and logs. Presently, not much is known about the ecology or life history of this species because it is found in such small numbers throughout its range. The species can survive in waters with some turbidity, but not in waters with a high amount of sediment pollution. One of the leading management actions aiding in the successful reproduction of this species is keeping the waters void of sediment pollution and habitat alterations. The northern madtom is also found along the Allegheny River system running from Canada through the Northeastern United States to Tennessee. However, over much of its range, the species is found in only a few streams/creeks in each state. In Canada, the species is confined to only four distinct locations: St. Clair River, Lake St. Clair, Thames River (Ontario), and Detroit River. The population status of these four locations has been classified as poor by Fisheries and Oceans Canada. In Pennsylvania, the northern madtom is only found in one creek on the far western edge of the state. Because of this restricted distribution across most of its range, the species has been labeled as critically imperiled. In Tennessee, the species is more common and is classified as vulnerable, instead. However, the Tennessee Wildlife Resources Agency places the northern madtom on the "Wildlife in Need of Management Proclamation" list. The sporadic distribution of the species across its range suggests that the northern madtom probably has very specific habitat requirements, so is vulnerable to habitat alterations. Ecology The diet of the northern madtom consists of small insects and invertebrates. However, because the species is found in such small numbers, no real evidence supports the specifics of their diet. Little is known as to the quality or quantity of what the northern madtom eats. The northern madtom is found in different habitats throughout its range. In the northern extent of its distribution, the species is found more in larger rivers and even in a few lentic environments such as Lake St. Clair. However, in the lower most stretches of its range, such as in Tennessee, the species is generally more common in small creeks and streams with a somewhat moderate current. Across all regions, the species tends to prefer habitat with sand, gravel, or rock substrates. The species is somewhat tolerant of turbidity, but avoids areas of high siltation. The northern madtom shares its habitat with several similar species ranging from the very similar mountain madtom to some