The peamouth (''Mylocheilus caurinus''), also known as the peamouth chub, redmouth sucker or northwestern dace, is a species of freshwater

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

from 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 ...

, the shiners, daces and minnows. This species 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 ...

Taxonomy

The peamouth is the only extant species in the genus ''Mylocheilus''. However, three

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

species are also 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

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Mylocheilus inflexus'' (

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 ...

, 1883) - Late Miocene/

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 ...

of Deer Butte Formation (Oregon),

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Glenns Ferry Formation The Glenns Ferry Formation is a Pliocene stratigraphic unit in the western United States. Outcrops of the formation in Hagerman Fossil Beds National Monument preserve the remains of seven fish species, five of which are extinct. These include the t ...

(Idaho) * †''

Mylocheilus robustus The peamouth (''Mylocheilus caurinus''), also known as the peamouth chub, redmouth sucker or northwestern dace, is a species of freshwater ray-finned fish from the Family (biology), family Leuciscidae, the shiners, daces and minnows. This species ...

'' ( Leidy, 1870) - Late Miocene/Early Pliocene of Deer Butte Formation (Oregon), Pliocene of the Glenns Ferry Formation (Idaho) * †'' Mylocheilus whitei'' Smith & Cossel, 2002 - Late Miocene (

Hemphillian The Hemphillian North American Stage on the geologic timescale is a North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 10,300,000 to 4,900,000 years BP. It is usually considered t ...

) of the Poison Creek Formation (Idaho) Mycau j0

Description

The peamouth is a slender fish, with a somewhat compressed body and a subterminal mouth, large eyes, a rounded snout and a forked tail. It has a dark back, contrasting with silvery underparts separated by two dusky, longitudinal stripes. The mouth is reddish at the corners where there are small barbels. When breeding the mature males develop a red stripe along the sides on the belly, mouth, gill cover and

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

base. The

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 ...

and 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 ...

each have 8 soft rays and the

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...

has 66–84 scales. They can grow to in total length.

Distribution

The peamouth occurs in western North America from the

Mackenzie River The Mackenzie River (French: ; Slavey language, Slavey: ' èh tʃʰò literally ''big river''; Inuvialuktun: ' uːkpɑk literally ''great river'') is a river in the Canadian Canadian boreal forest, boreal forest and tundra. It forms, ...

in the

North West Territories The Northwest Territories is a federal territory of Canada. At a land area of approximately and a 2021 census population of 41,070, it is the second-largest and the most populous of the three territories in Northern Canada. Its estimated pop ...

, the

Nass River The Nass River is a river in northern British Columbia, Canada. It flows from the Coast Mountains southwest to Nass Bay, a sidewater of Portland Inlet, which connects to the North Pacific Ocean via the Dixon Entrance. Nass Bay joins Portland I ...

and the

Peace River The Peace River () is a river in Canada that originates in the Rocky Mountains of northern British Columbia and flows to the northeast through northern Alberta. The Peace River joins the Athabasca River in the Peace-Athabasca Delta to form the ...

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

and 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 ...

drainage in

Washington state Washington, officially the State of Washington, is a state in the Pacific Northwest region of the United States. It is often referred to as Washington State to distinguish it from the national capital, both named after George Washington ...

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

and

Idaho Idaho ( ) is a landlocked U.S. state, state in the Pacific Northwest and Mountain states, Mountain West subregions of the Western United States. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington (state), ...

. It is relatively tolerant of salt water and this has allowed it to colonise rivers on

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian province of British Columbia. The island is in length, in width at its widest point, and in total area, while are of land. The island is the largest ...

and other islands off the coast of British Columbia. It has been introduced to the

Redwood National Park The Redwood National and State Parks (RNSP) are a complex of one List of national parks of the United States, United States national park and three List of California state parks, California state parks located along the coast of northern Cali ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

Habitat

The peamouth can be found in the shallow, weedy zones of lakes and rivers, where it is most common among vegetation. It is usually found near the bed in depths of less than , although in winter they will move to the deeper parts of lakes.

Biology

Young peamouths feed predominantly on micro-crustaceans which are also preyed on by the adult fish but their diet is expanded to include snails, adult aquatic and terrestrial insects and even the occasional small fish. The peamouth reaches sexual maturity at 3–4 years old, the males normally reaching it faster than the females. Spawning takes place in May and June when the water reaches temperatures of , and happens in streams or along the shores of lakes where there are gravel or stony substrates in shallow water which is within of the bank. The eggs adhere to rocks or other substrates. The fish may spawn several times in a season, and the timing of spawning is not fully understood. The spawning runs of the peamouth make an impressive natural spectacle as the brightly colored fish move into areas of warm, shallow, flowing water in large numbers. These schools attract many fish-eating predators. The newly hatched fry form schools near the shore, moving into deeper water later in the summer. Each female is normally attended by at least two males and can lay between 5,000 and 30,000 eggs, the amount being dependent on the age and size of the individual fish. The fish may spend the day in deeper water and move to the shallows to feed at night. They are preyed on by a variety of

piscivorous A piscivore () is a carnivorous animal that primarily eats fish. Fish were the diet of early tetrapod evolution (via water-bound amphibians during the Devonian period); insectivory came next; then in time, the more terrestrially adapted rept ...

mammals and birds, as well as by larger fish species. They may attain a life span of 8 years

Human use

They have been used as a food fish by people the past and are still fished for by anglers. In Bellevue City near Seattle has an online alert system which informs people when the peamouth appear to spawn in the local streams so that interested people can observe the spectacle, being informed by email whenever the fish are observed.

Hybridisation

Hybrids between the peamouth and the Northern pikeminnow (''Ptychocheilus oregonensis'') and the redside shiner (''

Richardsonius balteatus The redside shiner (''Richardsonius balteatus'') is a species of freshwater ray-finned fish belonging to the family Leuciscidae, the shiners, daces and minnows. This fish is found in the Western United States and British Columbia.Leo Nico, and Pa ...

'') have been recorded throughout North America. The latter hybrid was once described as ''Cheonda cooperi'' before its true nature was discovered.

References

{{Taxonbar, from=Q2706124 Pogonichthyinae Fish of North America Fish of the United States Fish described in 1836