The chiselmouth (''Acrocheilus alutaceus'') is an unusual

cyprinid Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest ve ...

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% ...

of western North America. It is named for the sharp hard plate on its lower jaw, which is used to scrape rocks for

algae Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from ...

. It is the sole member of the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

''Acrocheilus'' and is a close relative of the '' Gila'' western chubs.

Description

The chiselmouth's body plan generally follows the standard cyprinid form, generally elongated and slightly compressed. The snout is very blunt, with the lower jaw's plate (which consists of cornified epithelium) jutting out slightly. Coloration is rather drab, dark brown above and lighter lower down. Many individuals also have a pattern of black dots, and younger fish may have a dark area at the base of the tail. The single

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...

has 10 soft rays, while the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as s ...

and well-developed

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two e ...

s each have 9-10 rays. Chiselmouths can reach a length of 30 cm (12 in).

Distribution and habitat

Chiselmouths are typically found in warmer parts of streams and rivers in the drainages of the Columbia River,

Fraser River The Fraser River is the longest river within British Columbia, Canada, rising at Fraser Pass near Blackrock Mountain in the Rocky Mountains and flowing for , into the Strait of Georgia just south of the City of Vancouver. The river's annua ...

, and the

Harney-Malheur The Harney Basin is an endorheic basin in southeastern Oregon in the United States at the northwestern corner of the Great Basin. One of the least populated areas of the contiguous United States, it is located largely in northern Harney County ...

system of the Great Basin. Some are found in lakes, migrating into streams to spawn. Although abundant in many parts of their range, behavior remains little-known. Chiselmouth were among the fishes typically utilized by the

Nez Perce people The Nez Percé (; autonym in Nez Perce language: , meaning "we, the people") are an Indigenous people of the Plateau who are presumed to have lived on the Columbia River Plateau in the Pacific Northwest region for at least 11,500 years.Ames, ...

as food.

Diet

Young fish feed on surface

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...

s. When the chisel develops (at around 0.6 inches length), they shift to scraping, making short darting movements at the substrate to dislodge whatever is on it, and sucking it in. Although they consume filamentous algae, it seems to not be digested much despite a long coiled intestine, and their primary food actually consists of diatoms.

References

* * (1987): ''Fishes of the Great Basin'': 149–151. University of Nevada Press, Reno. * (1997): Phylogenetic Relationships of the Creek Chubs and the Spine-Fins: an Enigmatic Group of North American Cyprinid Fishes (Actinopterygii: Cyprinidae). ''Cladistics'' 13(3): 187–205. (HTML abstract) {{Taxonbar, from=Q3117415 Leuciscinae Chubs (fish) Fauna of Western Canada Fish of the Western United States Fish described in 1855 Freshwater fish of the United States Taxobox binomials not recognized by IUCN nl:Acrocheilus