The Colorado pikeminnow (''Ptychocheilus lucius'', formerly squawfish) is the largest
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 ver ...
fish of North America and one of the largest in the world, with reports of individuals up to 6 ft (1.8 m) long and weighing over 100 pounds (45 kg). Native to the
Colorado River
The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid watershed that encompasses parts of seven U.S. s ...
Basin of the southwestern
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
and adjacent
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
, it was formerly an important
food fish
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ing ...
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 known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...
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 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 found else ...
fish species:
bonytail chub
The bonytail chub or bonytail (''Gila elegans'') is a cyprinid freshwater fish native to the Colorado River basin of Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming in the southwestern United States; it has been extirpated fro ...
,
humpback chub
The humpback chub (''Gila cypha'') is a 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 dorsal fin, which i ...
, and
razorback sucker
The razorback sucker (''Xyrauchen texanus'') is a suckerfish found in rivers and lakes in the southwestern United States. It can grow to in length and is recognisable by the keel between its head and dorsal fin. It used to inhabit much of the C ...
. The Colorado pikeminnow is currently listed as vulnerable by the IUCN, 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 catego ...
is "critically imperiled".
Description
Like the other three species of pikeminnows, it has an elongated body reminiscent of the
pike
Pike, Pikes or The Pike may refer to:
Fish
* Blue pike or blue walleye, an extinct color morph of the yellow walleye ''Sander vitreus''
* Ctenoluciidae, the "pike characins", some species of which are commonly known as pikes
* ''Esox'', genus of ...
. 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 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 ...
. 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
A ...
'' in 1994, reported that such individuals were once common. Catches in the 1960s ranged up to 60 cm for 11-year-old fish, but by the early 1990s, maximum sizes reached no more than 34 cm. Biologists now consider the typical size of an adult pikeminnow to be between 4 and 9 pounds, and reports of the fish lately exceeding 3 feet in length are now in question.
Biology
Young pikeminnows, up to 5 cm long, eat
cladocera
The Diplostraca or Cladocera, commonly known as water fleas, are a superorder of small crustaceans that feed on microscopic chunks of organic matter (excluding some predatory forms).
Over 1000 species have been recognised so far, with many more ...
chironomid
The Chironomidae (informally known as chironomids, nonbiting midges, or lake flies) comprise a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae. Many specie ...
larvae, then shift to
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 ...
s around 10 cm long, gradually eating more fish as they mature. Once they achieve a length around 30 cm, 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 100 km or more. Spawning occurs around the summer solstice, with declining flows and increasing temperatures. Breeding males are bronze-colored and heavily covered with tubercles, 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. Upon hatching and swim-up, the small fry are entrained and carried 50–100 km downstream.
Breeding
As talked about briefly in the biology section, Colorado Pikeminnow tends to spawn in late July, early August in the Green River. A clear indicator of when these fish tend to reproduce is when the water temperature reaches over 18° C. The fish as previously stated migrate towards deep pools and rushing water to lay their eggs. Once a female lays her eggs, male Colorado Pikeminnow will follow the trial of eggs, dispersing semen. These eggs hatch at different rates based on the temperature of the water. When the water is around 20° C, eggs hatched within 3-5 days, and at a higher temperature of 25° C, eggs hatched at around 2-3 days. Along with the fast hatch rate, these eggs are also susceptible to movement. For example, looking at the Green River, one of a few remaining locations, eggs have been observed to move anywhere from 100 to 160 kilometers.
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 combi ...
White
White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White o ...
Yampa River
The Yampa River flows through northwestern Colorado in the 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 ...
s. They have been transplanted to the
Salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
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 ...
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 instillation 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. In specific, 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.
Population reduction efforts
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 used as a broad-spectrum insecticide, piscicide, and pesticide. It occurs naturally in the seeds and stems of several plants, such as the jicama vine plant, and the roots of several mem ...
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. Potassium permanganate was used to neutralize the rotenone, but concentrations were higher than expected and rotenone continued into the Dinosaur National Monument area.Restoring Colorado River Ecosystems (Island Press 2007)
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 as well as the only successful site for reintroduction was the Green River, more specifically the upper Green river. Fish up to 16 inches 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.