The Colorado pikeminnow (''Ptychocheilus lucius''), formerly known as the squawfish, 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 ...

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 ...

, the

dace A dace is a small fish that can be one of many different species. The unmodified name is usually a reference to the common dace (''Leuciscus leuciscus''). This, like most fish called "daces", belongs to the family Leuciscidae, mostly in subfami ...

chub Chub is a common fish name. It pertains to any one of a number of ray-finned fish in several families and general. In the UK, the term ''chub'' usually refers to the species '' Squalius cephalus''. In addition, see sea chub. In family Cyprinid ...

s, Eurasian minnows and related species. This is one of the largest leuciscids of

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 ...

and one of the largest in the world, with reports of individuals up to long and weighing over . Native to the

Colorado River The Colorado River () is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and in northern Mexico. The river, the List of longest rivers of the United States (by main stem), 5th longest in the United St ...

Basin of the southwestern

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and adjacent

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

, it was formerly an important

food fish Many species of fish are caught by humans and consumed as food in virtually all regions around the world. Their meat has been an important dietary source of protein and other nutrients in the human diet. The English language does not have a s ...

for both Native Americans and European settlers. Once abundant and widespread in the basin, its numbers have declined to the point where it has been

extirpated Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions. Local extinctions mark a chan ...

from the Mexican part of its range and was listed as endangered in the US part in 1967, a fate shared by the three other large Colorado Basin

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

fish species: bonytail chub,

humpback chub The humpback chub (''Gila cypha'') is a Endangered species act, federally protected fish that lived originally in fast waters of the Colorado River system in the United States. This species takes its name from the prominent hump between the head ...

, and

razorback sucker The razorback sucker (''Xyrauchen texanus'') is a suckerfish found in rivers and lakes in the southwestern United States and formerly northwestern Mexico. It can grow to in length and is recognisable by the keel between its head and dorsal fin. ...

. The Colorado pikeminnow is currently listed as vulnerable by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

, while its

NatureServe conservation status The NatureServe conservation status system, maintained and presented by NatureServe in cooperation with the Natural Heritage Network, was developed in the United States in the 1980s by The Nature Conservancy (TNC) as a means for ranking or categor ...

is "critically imperiled".

Description

Like the other three species of pikeminnows, it has an elongated body reminiscent of the pike. The cone-shaped and somewhat flattened head is elongated, forming nearly a quarter of the body length. Color grades from bright olive green on the back to a paler yellowish shade on the flanks, to white underneath. Young fish also have a dark spot on the

caudal 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 only ...

. Both the dorsal and anal fins typically have 9 rays. The

pharyngeal teeth Pharyngeal teeth are teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species otherwise lacking teeth.community elders, interviewed by the ''

Salt Lake Tribune ''The Salt Lake Tribune'' is a newspaper published in the city of Salt Lake City, Utah. The ''Tribune'' is owned by The Salt Lake Tribune, Inc., a non-profit corporation. The newspaper's motto is "Utah's Independent Voice Since 1871." History ...

'' in 1994, reported that such individuals were once common. Catches in the 1960s ranged up to for 11-year-old fish, but by the early 1990s, maximum sizes reached no more than . Biologists now consider the typical size of an adult pikeminnow to be between , and reports of the fish lately exceeding in length are now in question. Colorado_Pikeminnow_OdySea_Aquarium

Biology and reproduction

Young pikeminnows, up to long, eat

cladocera The Diplostraca or Cladocera, commonly known as water fleas, is a superorder (biology), superorder of small, mostly freshwater crustaceans, most of which feed on microscopic chunks of organic matter, though some forms are predatory. Over 1000 sp ...

ns,

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

s, and

chironomid Chironomidae , commonly known as non-biting midges or chironomids , are a family of Nematoceran flies with a global distribution. They are closely related to the families Ceratopogonidae, Simuliidae, and Thaumaleidae. Although many chironomid s ...

larvae, then shift to

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 around long, gradually eating more fish as they mature. Once they achieve a length around , they feed almost entirely upon fish. This fish has an ontogenetic separation of life history stage. The altricial young emerge from whitewater canyons, enter the drift as sac-fry, and are transported downstream. Habitat for the young fish is predominately alongshore backwaters and associated shorelines of more alluvial reaches of the turbulent and turbid rivers of the Colorado system. In contrast, adults reside in more well-defined channels, where they seek eddy habitats and prey on suckers and minnows. Colorado pikeminnows are potamodromous, making freshwater spawning migrations to home in on their natal areas. These migrations can begin as upstream or downstream movements, depending on the location of home range of individuals, and may involve or more. Spawning occurs around the summer solstice, with declining flows and increasing temperatures. Breeding males are bronze-colored and heavily covered with

tubercles In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection, b ...

, while females are generally larger, lighter in color and with fewer tubercles. As the fish reach the spawning location, they stage in deeper pools and eddies and make spawning runs into nearby runs and deep riffles, where the adhesive eggs are released. Once a female lays her eggs, male Colorado Pikeminnow will follow the trail of eggs, dispersing semen. These eggs hatch at different rates based on the temperature of the water. When the water was around , eggs hatched within 3–5 days, and at a higher temperature of , eggs hatched in around 2–3 days. Upon hatching and swim-up, the small fry are entrained and carried downstream.

Range

The species was once found throughout the Colorado Basin, so occurred in Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming, as well as in Mexico. Damming and habitat alterations have confined the species to the upper Colorado drainage; currently, remnant populations are known from the

Green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a com ...

, Gunnison,

White White is the lightest color and is achromatic (having no chroma). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully (or almost fully) reflect and scatter all the visible wa ...

San Juan San Juan, Spanish for Saint John (disambiguation), Saint John, most commonly refers to: * San Juan, Puerto Rico * San Juan, Argentina * San Juan, Metro Manila, a highly urbanized city in the Philippines San Juan may also refer to: Places Arge ...

, and

Yampa River The Yampa River flows through northwestern Colorado, United States. Rising in the Rocky Mountains, it is a tributary of the Green River and a major part of the Colorado River system. The Yampa is one of the few free-flowing rivers in the weste ...

s. They have been transplanted to the

Salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

and

Verde River The Verde River ( Yavapai: Haka'he:la) is a major tributary of the Salt River in the U.S. state of Arizona. It is about long and carries a mean flow of at its mouth. It is one of the largest perennial streams in Arizona. Description The ri ...

s, both within their native range.

Threats

The Colorado Pikeminnow was once a species of fish that resided in much of the Colorado River Basin. Due to human impacts and the introduction of non-native fish species, the population has receded to the upper basin. According to the ''Native Aquatic Species Conservation in Arizona,'' the installation of dams has altered the fish's movement. Along with this, dewatering, altered stream flow, channel morphology, water quality, water chemistry, silt loads, and introduction of non-native fish have challenged the Colorado Pikeminnow (Sublette et al. 1990, Muth and Snyder 1995). It has also been hypothesized that due to the installation of dams, the change in water temperature has altered breeding tendencies. Breeding is water temperature dependent, meaning the temperature of the water must be perfect for spawning to occur. Changes in these conditions have caused breeding grounds to change. Non-native fish have posed a threat in both predation and competition for resources. With the introduction of various invasive catfish species, Greenback cutthroat trout, and red shiner (''Cyprinella lutrensis''), the population of Colorado Pikeminnow has declined drastically. A study was conducted analyzing the factors of recruiting young Colorado Pikeminnow. In particular, it was found that red shiners feed on the larvae of Colorado Pikeminnow in vivo. Additionally, land managers in the past have attempted to reduce the native fish population of the Colorado Basin in favor of sport fishing. In the mid-1960s, the federal government poured the poison

rotenone Rotenone is an odorless, colorless, crystalline isoflavone. It occurs naturally in the seeds and stems of several plants, such as the jicama vine, and in the roots of several other members of the Fabaceae. It was the first-described member of the ...

into the Green and San Juan Rivers, attempting to create an environment supportive of non-native sportfish. In September 1962, the Green River was poisoned beginning upstream of Flaming Gorge. The poison worked downstream for 3 days until it reached upstream of

Dinosaur National Monument Dinosaur National Monument is an American national monument located on the southeast flank of the Uinta Mountains on the border between Colorado and Utah at the confluence of the Green River (Colorado River tributary), Green and Yampa River, Y ...

Potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, which dissolves in water as K+ and ions to give an intensely pink to purple solution. Potassium permanganate is widely us ...

was used to neutralize the rotenone, but concentrations were higher than expected and rotenone continued into the Dinosaur National Monument area.

Restoration efforts

Recovery efforts are focused on operating dams to create more natural flow patterns, improving fish passage up- and downstream, and restricting stocking of non-native fish to reduce ecological interactions. In Arizona, hatcheries are in the process of restocking the Upper basin with Colorado pikeminnow. According to the ''Native Aquatic Species Conservation in Arizona,'' it was found that small fish could not avoid predation and that the only successful site for reintroduction was the Green River, more specifically the upper Green River. Fish up to long have been released in the hopes of increasing the survival rate of the released Colorado pikeminnow. There has been evidence that population numbers are increasing in the San Juan River. The Colorado pikeminnow was one of the first species listed under the

Endangered Species Act The Endangered Species Act of 1973 (ESA; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting and conserving imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of e ...

in 1973 as endangered, due to its

extirpation Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with extinction, global extinctions. Local extinctions ...

from the Lower Colorado River Basin following damming in the early 20th century. A stocking program in the

has been discontinued due to futility, and current conservation efforts are aimed at preserving pikeminnow populations in three subbasins within the Upper Colorado River: the Green River, the Upper Colorado River and the San Juan River. A draft recovery plan published in 2022 projected a cost of nearly US$180 million over 15 years to recover the Colorado pikeminnow through management of water flow, maintenance of fish passages and control of nonnative species, among other measures.

References

External links

* William F. Sigler and John W. Sigler, ''Fishes of Utah'' (University of Utah Press, 1996), pp. 109–114
USFWS Upper Colorado Endangered Fish Recovery Program

* ttp://ecos.fws.gov/tess_public/SpeciesReport.do?groups=E&listingType=L&mapstatus=1 USFWS List of Fish Listed under Endangered Species Act* Muth, R.T. and Snyder, D.E. 1995. Diets of young Colorado squawfish and other small fish in backwaters of the Green River, Colorado and Utah. The Great Basin Naturalist 55 (2): 95–104. {{Authority control Ptychocheilus Fish of North America Endangered fauna of the United States Taxa named by Charles Frédéric Girard Fish described in 1856 ESA endangered species