Noturus exilis, also called the slender madtom is a species of the Ictaluridae

Ictaluridae

The Ictaluridae, sometimes called Ictalurids, are a family of catfish native to North America, where they are important food fish and sometimes as a sport fish. They include fish commonly known as bullheads, madtoms, channel catfish, and blue catfish....

 family of catfish

Catfish

Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...

. The Ictaluridae family includes bullheads, madtoms, channel catfish, and blue catfish. Noturus exilis is found in the central portion of the Mississippi River

Mississippi River

The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...

 basin, but is most abundant in Ozarkian streams. Slender Madtoms occur west of the Mississippi River in the Ozarks of Oklahoma

Oklahoma

Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...

, Arkansas

Arkansas

Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...

, and Missouri

Missouri

Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...

 north to southern Wisconsin

Wisconsin

Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...

 and Minnesota

Minnesota

Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

. It also occurs east of the Mississippi River in the uplands of Alabama

Alabama

Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...

, Tennessee

Tennessee

Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...

, and Kentucky

Kentucky

The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...

 in the Tennessee, Cumberland, and Green drainages. Nelson first described Noturus exilis in 1876. The Tennessee distribution ranges from the Tennessee River between west and middle Tennessee to the Highland Rim and Nashville Basin. A slender madtom is moderately large with a terminal to sub terminal mouth, flat head, small eyes, and black marginal bands on the median fins. Most slender madtoms are less than 90 millimetres (3.5 in). Noturus flavus

Noturus flavus

Noturus flavus -Description:Stonecats are small, slender, flat-headed catfishes, with the adipose fin keellike and continuous with the dorsal fin except for a shallow notch. The upper jaw projects beyond the lower jaw and the tooth pad on the upper jaw has a narrow, crescent-shaped extension on...

and Noturus nocturnus

Noturus nocturnus

The common name of Noturus nocturnus is the freckled madtom. It is one of the 324 fish species found in Tennessee....

are rather similar in shape and coloration to Norturus exilis. Slender madtoms inhabit small to medium sized streams, in riffle and flowing pool habitats with coarse gravel to slab rock substrates. The presence of a shelter object, such as a large rock, seems to be important in habitat selection.

Distribution

Slender madtoms inhabit two disjunct areas of the Central Highlands: one in the Ozark Highlands ranging from eastern Kansas and Oklahoma to the southern tip of Illinois and including most of Missouri and northwest Arkansas, and another in the Eastern Highlands, from middle Tennessee and part of southeastern Kentucky, ranging into northern Alabama and Mississippi. The slender madtom also occurs as several smaller, isolated populations in Iowa, Illinois and southern Wisconsin and Minnesota. Slender madtoms have seen a decrease in population size from their previous habitat ranges. Due to habitat alteration along the small streams of the Tennessee drainage, this species may be in great danger of extirpation from Mississippi.It has also declined in the northern part of its range in Wisconsin, due primarily to agricultural runoff or alterations in river flow due to dams. The slender madtom's range has mostly likely decreased due to dam construction, channelization, and agricultural runoff.

Ecology

The slender madtom's diet consists of midges, mayflies, caddieflies, isopods, amphipods, and copepods, but ephemeroteran naiads and chironomid larve make up a majority of their diet. Smallmouth bass

Smallmouth bass

The smallmouth bass is a species of freshwater fish in the sunfish family of the order Perciformes. It is the type species of its genus...

 (Micropterus dolomieu) is a known predator of slender madtoms, which may be one reason why slender madtoms prefers a nocturnal lifestyle, seeking cover during the day when this visual predator is on the prowl. Embryo predation by Orconectes virilis

Orconectes virilis

Orconectes virilis is a species of crayfish known as the virile crayfish or the northern crayfish.-Ecology:Orconectes virilis can be found under stones in lakes, streams and wetlands, where they hide from predators, such as fish. They are identified by the brown of rust-red carapace and large...

(virile crayfish), Campostoma anomalum

Campostoma anomalum

-Introduction:This is a description of a monitoring plan that has been laid out for a commonly known species Campostoma anomalum or Central Stoneroller...

(central stoneroller) and Etheostoma caeruleum (rainbow darter) has also been noted. The Slender Madtom and the Orangethroat Darter (Etheostoma spectabile) also compete for and share the same diet.The slender madtom inhabits the rocky riffles and pools of creeks and small rivers, spending much of the day hiding under large rocks and emerging to feed at night. Slender madtoms feed preferably after dusk and before dawn. Slender Madtoms have also been observed in high percentages in vegetated patches and backwaters during late summer. The slender madtom can be found in streams with current speeds from 8-92 cm/sec and can be found at depths between 5-42cm. The slender madtom has never been a strong swimmer, which has reduced their dispersal over the centuries.

Life history

Mayden and Burr found that reproductive activity was concentrated from mid June through July at water temperatures of 23.5-29° C in Southern Illinois.
Large lowland rivers, such as the Missouri River and Mississippi River, have high silt loads, covering the gravel and rocks that madtoms require for nesting and diurnal refugia. Spawning sites are usually cavities excavated under large rocks, usually in pool areas. Nests have been found to contain 27-74 eggs and are protected by the male until the yolk sac absorbed by the juveniles. Hatching occurs within eight to nine days in 25°C water. Individuals are one half the length of a one year old by three weeks. Summer is the season of greatest growth, particularly during the first two years of life, and in winter growth slows to a near standstill. Females are capable of spawning their first summer, especially in harsher northern conditions, as long as a critical size is attained (approximately 50 mm in southern Illinois). In contrast, males do not breed until two years of age. The ratio of ovary weight to adjusted body weight (GSI) increased in females in fall and spring, with greater rates of growth in mature adults. Slender madtom are usually 3 inches or less in size with a maximum of about 4 inches. Slender madtoms can live up to 5 years of age, but most have been collected between 1-3 years old. Adult slender madtoms are weak dispersers, with poor swimming abilities, a characteristic that may have contributed to the existence of two disjoint populations of the species.

Current management

Populations across the slender madtom's range have declined since the late 1970s. The species is nearly extirpated in Wisconsin, although once more widespread there than in Minnesota. Causes for decline may include siltation and turbidity in farming areas, and the dewatering of habitats by hydropower operations. Poor farming practices near streams could be contributing sediments and large amounts of nutrients into streams inhabited by slender madtoms and other species that make the overall ecosystem uninhabitable. Human uses have degraded the habitat and lively hood of the slender madtom and associated species. Predation and intraspecific and interspercific competition may also affect the survivorship of slender madtoms. The Minnesota Department of Natural Resources has done stream surveys but found very few slender madtom specimens. The slender madtom has not had a population assessment at the national level. The slender madtom is classified as endangered in Mammoth Cave National Park. The slender madtom is also classified as endangered in Wisconsin. No current management is being done to protect the slender madtom from outside pollutants and other detrimental factors. Some state agencies have surveyed streams for slender madtoms, but no management plan has been put in place. Sufficient research has not been collected on the slender madtom to determine the best method to create new habitat or restore the previous habitat to benefit the slender madtom for decades to come.