The largest of the redhorse (Moxostoma) species (3) (4), the greater redhorse (Moxostoma valenciennesi) is a large, stout freshwater fish with a dark brown to copper back, yellowish sides and a whitish belly (2) (3) (4) (5). The scales on the back and sides have a dark spot at their base (3) (5) (6). The greater redhorse’s tail fin is red, and the other fins are yellow to orange or reddish (2) (3) (4) (5) (6).
The greater redhorse has a large head and a large mouth, with thick lips that are covered in folds (3) (5) (6). In adults, the dorsal fin has a straight or slightly convex edge (3) (4) (6), and the tail fin is large and forked, with two pointed lobes (5). The female greater redhorse is generally larger than the male (2), and breeding males have large, white tubercles on the tail fin and anal fin (2) (3).
Like other fish in the Cyprinidae family, the greater redhorse does not have teeth in its jaws, instead processing food using specialised bones in the throat (7). Known as ‘pharyngeal teeth’, these are thin and bladelike in this species (5) (6).
- Moxostoma aureolum, Moxostoma rubreques.
- Length: up to 80 cm (2)
- up to 5.9 kg (3)
Greater redhorse biology
The greater redhorse usually spawns between May and July, depending on the location (3) (4) (11) (12). On arriving upstream at the spawning grounds, the males congregate and hold territories, generally moving about slowly and often nudging each other. The females visit the males when ready to spawn (3) (12). This species may spawn in groups of two to seven males and one or two females (2) (11), or in trios of two males to one female (3) (12). The male greater redhorses flank a female on either side, rolling over each other and the female while the tail and dorsal fins are vibrated and the eggs and sperm are released over the substrate (2) (11) (12).
The female greater redhorse is estimated to release around 32,000 to 72,000 yellow eggs, which hatch in about 6 to 8 days (11) (13). Both male and female greater redhorses are thought to become mature at around 5 to 6 years old (3) (11). After spawning, the adult greater redhorses move back downstream to areas of deeper water and slower current (10).
The diet of the greater redhorse comprises a variety of invertebrates, including aquatic insects, molluscs and crustaceans (3) (4), as well as some plant material (3). This species is likely to forage mainly on the river bottom (3) (8).
Greater redhorse range
The greater redhorse occurs in North America, from Ontario and Quebec in Canada and northern Minnesota in the United States, south to Indiana, Ohio and Kentucky. It has been recorded in the Great Lakes-St. Lawrence River, Hudson Bay (Red River) and Mississippi River basins (2) (3) (4) (5).
Although it has also been reported south to the Ohio River in Kentucky (2) (3) (5), the greater redhorse may now have disappeared from this state (3).
Greater redhorse habitat
This freshwater fish is usually found in medium to large rivers and sometimes also in lakes (2) (3) (5) (8). The greater redhorse generally requires clear water, without much silt (3), and prefers parts of the river with sandy or rocky pools, or areas of moderate to fast current (2) (3) (5) (9).
The greater redhorse typically migrates upstream to spawn over gravel, cobble or pebble substrates in shallow riffles (2) (3) (10) (11) (12).
Greater redhorse status
The greater redhorse has yet to be classified by the IUCN.
Greater redhorse threats
Although it is widely distributed, the greater redhorse occurs in relatively small, disjunct populations and has been declining in parts of its range (3) (5) (8). Its numbers may have stabilised or even in increased in some areas in recent years due to improvements in water quality, but smaller, more isolated populations and those on the edges of its range are more vulnerable (3) (8).
The greater redhorse is particularly sensitive to alterations to its habitat, with the main threats coming from siltation and pollution, which may reduce its prey and also reduce the quality of its spawning habitats. The habitat of this species may be further degraded by dam construction, river channelization, alterations to flow regimes, and the removal of riverside vegetation. Infrastructure such as dams can also create barriers along spawning migration routes (3) (8).
The greater redhorse is not commonly targeted by anglers, but low numbers may be caught in some areas (3) (8).
Greater redhorse conservation
The greater redhorse is listed as a ‘Species of Concern’ by the U.S. Fish and Wildlife Service (14). There have been few specific conservation measures targeted at this species, but it is likely to have benefitted from general improvements in water quality and from efforts to restore stream habitats and riverside vegetation, as well as to improve fish passage at dams (3) (8).
Recommended conservation measures for the greater redhorse include undertaking habitat restoration, and protecting its habitat from pollution and from erosion problems, which can lead to siltation (3). Detailed information on this species is lacking, so further research is required to determine the extent of its distribution, to monitor its population trends, and to increase the knowledge of its habitat requirements, diet, movements and life history (3) (8).
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- Anal fin
- In fish, an unpaired fin on the under surface of a fish, behind the anus.
- Diverse group of animals with jointed limbs and a hard chitinous exoskeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
- Dorsal fin
- The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans (whales, dolphins and porpoises).
- Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
- A diverse group of invertebrates, mainly marine, that have one or all of the following; a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.
- Light rapids where water flows across a shallow section of river.
- The production or depositing of eggs in water.
- An area occupied and defended by an animal, a pair of animals or a group.
- Small, rounded, wart-like bumps on the skin or on a bone.
Integrated Taxonomic Information System (ITIS) (June, 2011)
FishBase - Greater redhorse, Moxostoma valenciennesi (June, 2011)
NatureServe Explorer - Moxostoma valenciennesi (June, 2011)
Werner, R.G. (2004) Freshwater Fishes of the Northeastern United States. Syracuse University Press, New York.
Page, L.M. and Burr, B.M. (1991) A Field Guide To Freshwater Fishes of North American North of Mexico. Houghton Mifflin Company, New York.
Smith, P.W. (2002) The Fishes of Illinois. University of Illinois Press, Champaign, Illinois.
Campbell, A. and Dawes, J. (2004) Encyclopedia of Underwater Life. Oxford University Press, Oxford.
Healy, B.D. (2002) Conservation Assessment for the Greater Redhorse (Moxostoma valenciennesi). USDA Forest Service, Cass Lake, Minnesota. Available at:
Yoder, C.O. and Beaumier, R.A. (1986) The occurrence and distribution of river redhorse, Moxostoma carinatum and greater redhorse, Moxostoma valenciennesi in the Sandusky River, Ohio. The Ohio Journal of Science, 86(1): 18-21.
Bunt, C.M. and Cooke, S.J. (2001) Post-spawn movements and habitat use by greater redhorse, Moxostoma valenciennesi. Ecology of Freshwater Fish, 10(1): 57-60.
Cooke, S.J. and Bunt, C.M. (1999) Spawning and reproductive biology of the greater redhorse, Moxostoma valenciennesi, in the Grand River, Ontario. Canadian Field-Naturalist, 113(3): 497-502.
Jenkins, R.E. and Jenkins, D.J. (1980) Reproductive behavior of the greater redhorse, Moxostoma valenciennesi, in the Thousand Islands region. Canadian Field-Naturalist, 94: 426-430.
Bunt, C.M. and Cooke, S.J. (2004) Ontogeny of larval greater redhorse (Moxostoma valenciennesi). American Midland Naturalist, 151(1): 93-100.
U.S. Fish and Wildlife Service: Species Profile - Greater redhorse (Moxostoma valenciennesi) (June, 2011)