River Redhorse

Moxostoma carinatum

SARA Status
No Status
NS
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

SARA Status

  • No Status NS
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX
COSEWIC Status
Not at Risk
NR
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

COSEWIC Status

  • Not at Risk NR
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX

Description

The River Redhorse (Moxostoma carinatum) is a large sucker in the family Catostomidae. It has also been referred to as the Big-sawed Sucker, River Mullet, Greater Redhorse, Redfin Redhorse and Redhorse Sucker. River Redhorse has the following characteristics:

  • large, laterally compressed body;
  • adults measure between 500 and 700 mm in length;
  • subterminal mouth and heavy pharyngeal arch with molariform teeth;
  • deeply folded lips without transverse ridges or papillae (bumps);
  • straight or slightly concave single dorsal fin and a forked caudal fin
  • red-tinted caudal and dorsal fins, and orange to reddish lower fins;
  • white belly, brown or olive green back and brassy, yellowish-green or coppery sides;
  • dark, crescent-shaped spots on each scale;
  • tubercles present on the snout, anal and caudal fins of spawning males; and
  • caudal peduncle scale count is usually 12, while the count along the lateral line is 42 to 47.

Habitat

The River Redhorse occurs throughout the central and eastern Mississippi River system and the Gulf Slope from Florida to Louisiana. In Canada, its distribution is characterized by disjunct populations in southern and eastern Ontario and southern and southwestern Quebec. This species has declined considerably over much of its range in the last 100 years. In Ontario, populations still occur in the Grand, Trent, Thames, Mississippi, Madawaska rivers and the Bay of Quinte, and recent data suggest a wider distribution in the Ottawa River watershed than previously documented. In Quebec, it also occurs in the Colounge, Gatineau, Noire and Richelieu river systems into Quebec. This fish appears to no longer exist in the Ausable, Châteauguay and Yamaska rivers.

In Canada, the River Redhorse lives in medium- to large-sized rivers. In the late spring, fish migrate from pool habitats with slow currents and abundant vegetation to shallow areas with moderate to swift flow, riffle-run habitats and coarse (gravel, cobble) substrates. Spawning occurs at temperatures between 17 and 20ºC and ritualized spawning displays have been observed. Fertilized eggs hatch within five to six days depending on the temperature. Larvae are dispersed by drifting to suitable rearing habitats. The age at maturity is older than in southern populations, ranging between five and ten years. Maximum age is 28 years in Canada.

Threats

Due to its narrow range of habitat preferences, spawning requirements and intolerance of high turbidity, siltation and pollution, the River Redhorse is susceptible to a number of threats. Habitat fragmentation can alter habitat conditions, resulting in restricted movements of individual fish and limited gene flow between populations. Also, changes in flow regime and siltation of spawning habitats may reduce recruitment. Agricultural, industrial and municipal activities that affect water quality (increased sediment load, excessive nutrients) also adversely impact this species. Other suspected threats include the effects of climate change, invasive species, disease and incidental harvest.

Further Information

For more information, visit the SARA Registry.

River Redhorse

River Redhorse

Moxostoma carinatum
Illustration © J. R. Tomelleri

Scientific Name: Moxostoma carinatum
SARA Status: Special Concern
COSEWIC Status: Special Concern
Region: Ontario and Quebec

Map showing distribution of River Redhorse, in Canada, as described in the following paragraph

Distribution of River Redhorse, in Canada.

Did You Know?

The diet of the River Redhorse consists of crayfishes, insect larvae and other benthic invertebrates. It also feeds extensively on molluscs. Its large teeth allow it to crush the shells of these organisms.

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