The chiselmouth (''Gila alutacea'') is a species of freshwater ray-finned fishes belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Leuciscidae Leuciscidae is a family of freshwater ray-finned fishes, formerly classified as a subfamily of the Cyprinidae, which contains the true minnows. Members of the Old World (OW) clade of minnows within this subfamily are known as European minnow ...

. This fish is found in western

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

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

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

Taxonomy

The chiselmouth was first formally described as ''Acrocheilus alutaceus'' in 1855 by

Louis Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he recei ...

and Charles Pickering with its type locality given as

Willamette Falls The Willamette Falls is a natural waterfall in the Northwestern United States, northwestern United States, located on the Willamette River between Oregon City, Oregon, Oregon City and West Linn, Oregon. The largest waterfall in the Northwest ...

, Oregon City,

Clackamas County, Oregon Clackamas County ( ) is one of the List of counties in Oregon, 36 counties in the U.S. state of Oregon. As of the 2020 United States census, 2020 census, the population was 421,401, making it Oregon's third-most populous county. Its county sea ...

and Wallawalla River at Whitman, then part of Walla Walla County. Agassiz and Pickering classified this species in the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Acrocheilus'', of which it was considered the only extant species. In addition to ''A. alutaceus'', an extinct species, '' Acrocheilus latus'' (

Cope A cope ( ("rain coat") or ("cape")) is a liturgical long mantle or cloak, open at the front and fastened at the breast with a band or clasp. It may be of any liturgical colour. A cope may be worn by any rank of the Catholic or Anglican clerg ...

, 1870) is known from the

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

and

Early Pliocene Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican d ...

-aged Glenns Ferry & Ringold Formation of Idaho and Washington. ''Acrocheilus'' is now considered to be a

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

of '' Gila'', within the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Laviniinae Laviniinae is a subfamily of freshwater ray-finned fishes belonging to the family Leuciscidae, the family which includes the daces, chubs, Eurasian minnows and related fishes. Members of this subfamily are known as western chubs or the wester ...

of the family

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 Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

) 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 on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

has 10 soft rays, while the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

and well-developed

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

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 The Columbia River (Upper Chinook language, Upper Chinook: ' or '; Sahaptin language, Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river headwater ...

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

, and the Harney-Malheur system of the

Great Basin The Great Basin () is the largest area of contiguous endorheic watersheds, those with no outlets to the ocean, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja Californi ...

. 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 Perce (; Exonym and endonym, autonym in Nez Perce language: , meaning 'we, the people') are an Indigenous people of the Plateau who still live on a fraction of the lands on the southeastern Columbia River Plateau in the Pacific Northwes ...

as food.

Diet

Young fish feed on surface

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

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

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

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) {{Authority control Gila (fish) 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