Margined Madtom
Noturus insignis
Distribution: The margined madtom is native to rivers and streams on the eastern slope of the Appalachian Mountains from New York south to Georgia. Its range also includes the St. Lawrence River watershed and the southeastern drainages of Lake Ontario. In New Hampshire, margined madtoms are found in southern Merrimack River tributaries and coastal watersheds.
Description: A small species of catfish with blue eyes and an adipose fin that is fused to the caudal fin. Yellowish to grey in color, margined madtoms are lighter in appearance than the usually darker colored bullheads.
Habitat: Margined madtoms live in rocky sections of medium sized streams and small rivers, where they can be locally very abundant.
Life History: Female madtoms lay clusters of eggs under stones in the quiet sections of riffles, after which the eggs are defended by the males. Madtoms feed on invertebrates living in the spaces between rocks and boulders. They are considered moderately tolerant of pollution. The pectoral spines of margined madtoms contain a venom gland capable of causing a painful sting. The species was likely introduced into New Hampshire due to its past use as a baitfish. The use of margined madtom as bait is now illegal.
Origin: Likely introduced
Conservation/Management: Margined madtoms have a relatively restricted distribution and are considered vulnerable to extirpation in New York, Virginia, and Georgia. Populations in the St. Lawrence drainage are listed as critically imperiled. Margined madtoms in New Hampshire appear to be expanding their range. Margined madtoms often share habitat with longnose dace in New Hampshire. The level of competition between the two species is not well understood. The shallow riffle habitat in which these species occur is vulnerable to flow alteration due to water withdrawal or increased impervious surfaces in a watershed. Changes in the relative abundance of margined madtoms versus longnose dace may be used as a potential indicator for identifying watersheds with altered flow regimes.