The Black Redhorse (or duquesnii) is a species of freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 fish endemic to Ontario

Ontario

Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

 and the eastern half of the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, where it lives in stream

Stream

A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

s and small to medium river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

s.

A bottom-feeder, it feeds on microcrustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, aquatic insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, detritus

Detritus

Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...

, and algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

. The black redhorse spawns in the spring.

This species has been identified as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). It is currently being considered for listing under the federal Species at Risk Act (SARA).

The Black Redhorse (Moxostoma duquesnei) is a member of the Sucker family (Catostomidae) and has the following characteristics:

• Laterally compressed body.
• Long rounded snout which overhangs inferior mouth.
• Narrow upper lip and thick, slightly concave lower lip.
• Has 43 to 51 lateral line scales.
• Club-shaped pharyngeal teeth
  Pharyngeal teeth
  Pharyngeal teeth are teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species lacking teeth.Popular aquarium fish such as goldfish and loaches have these structures. Members of the Botia genus such as clown loaches are known to make distinctive clicking...
  
  .
• Dorsal surface and upper sides are grey or olive brown with a silver-blue overtone; sides are lighter and usually silvery blue; ventral surface is silver to milky white.
• All fins are slate grey.
• Scale edges are dark.
• Females show little or no spawning colour, males have bold longitudinal stripes of black and colour (orange to pink) along their sides.
• Maximum known length is 66 cm; maximum weight is 3.2 kg. ^{see reference #1}

Distribution

The Black Redhorse has a wide, but disjunct, distribution in eastern North America. It is found from Alabama and Mississippi in the south to Ontario and Michigan in the north, and from New York in the east to Oklahoma and Minnesota in the west. In Canada, it is limited to southwestern Ontario where it occurs in only six watersheds. In the Lake Huron drainage, it is found in the Bayfield River, Maitland River and Ausable River watersheds. In the Lake Erie drainage, it is known from the Catfish Creek (extirpated) and Grand River watersheds. It is also present in the Thames River watershed in the Lake St. Clair drainage.

Habitat and Life History

The Black Redhorse usually lives in moderately sized rivers and streams, 25 to 130 m wide, up to 1.8 m in depth, and with generally moderate to fast currents. It is rarely found associated with aquatic vegetation. Substrates include rubble, gravel, sand, boulders and silt. In summer, they generally prefer pools and overwinter in deeper pools. In the spring, Black Redhorse migrate to spawning habitats. Spring spawning has been observed in riffle habitats at water temperatures between 15°C and 21°C, and over a variety of substrates from fine gravel to large cobble. Eggs are nonadhesive and range in size from 2.6 to 2.9 mm. The age at maturity is between two and six years. Lifespan increases with latitude and some individuals reach 16 years of age.

Diet

Adult Black Redhorse are bottom feeders and eat crustaceans and insects. The younger fish (less than 65 mm) are thought to prefer plankton

Plankton

Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

.

Threats

The availability of suitable habitat limits the distribution of the Black Redhorse in Canada, rendering its distribution highly fragmented. Habitat may be altered or impaired through urbanization and agricultural activities that increase siltation, turbidity, and change flow regimes. Its restricted spawning habitat preferences make recruitment vulnerable to changes in flow regime. Dams and impoundment of riverine habitats also restrict movements of fish. Incidental catches of Black Redhorse by sport fishers have been reported and may impact populations.

Similar Species

There are a total of seven Redhorse species in Canada (no information is available here for American Redhorse species), and the Black Redhorse is distinguishable based on a combination of tail colour, lip morphology and lateral line scale count. Black and Golden (M. erythrurum) Redhorses are extremely difficult to distinguish from each other.