The Black Redhorse…a Species at Risk in Ontario

This species has been identified as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). It has been considered for listing under the federal Species at Risk Act (SARA). It will not be listed under the SARA. Protection is, however, afforded through the federal Fisheries Act.

General Description

Moxostoma duquesnei

© J. R. Tomelleri

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;
• 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; and
• Maximum known length is 66 cm; maximum weight is 3.2 kg.

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.

Black Redhorse Distribution 

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 15o and 21oC, 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.

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, 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.

Text Sources: COSEWIC Status Report 2005.

For more information, visit the SARA Registry website at www.SARAregistry.gc.ca.