The Rio Grande Chub (''Gila pandora'') is a
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 verte ...
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 li ...
endemic to the
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 territorie ...
. It inhabits the upper
Rio Grande
The Rio Grande ( and ), known in Mexico as the Río Bravo del Norte or simply the Río Bravo, is one of the principal rivers (along with the Colorado River) in the southwestern United States and in northern Mexico.
The length of the Rio G ...
and
Pecos River
The Pecos River ( es, Río Pecos) originates in north-central New Mexico and flows into Texas, emptying into the Rio Grande. Its headwaters are on the eastern slope of the Sangre de Cristo mountain range in Mora County north of Pecos, New Mexico ...
systems in
Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...
,
New Mexico
)
, population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano)
, seat = Santa Fe
, LargestCity = Albuquerque
, LargestMetro = Tiguex
, OfficialLang = None
, Languages = English, Spanish ( New Mexican), Navajo, Ker ...
and
Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
. The Rio Grande Chub is native to most of its current range including all three of the states it can be found in. There are non-native populations that currently inhabit Coyote Creek, the Mora River, the Sapello River and other areas in New Mexico. There are currently no studies showing how the Rio Grande Chub is impacting waterways in its non-native range.
It has also been proposed that this fish is native to the Canadian River in New Mexico but this has not been proven. It is possible it was introduced there.
Natural hybridization can occur between the Rio Grande Chub and the
Longnose dace
The longnose dace (''Rhinichthys cataractae'') is a freshwater minnow native to North America. ''Rhinicthys'' means snout fish (reference to the long snout) and ''cataractae'' means of the cataract (first taken from Niagara Falls). Longnose dace ...
(''Rhinichthys cataractae'').
Physical Characteristics
Physical characteristics that can be used to identify the Rio Grande Chub include the head, eyes, tail, and size. Adults of this species can grow as large as 30 centimeters however they are typically much smaller. In Colorado, they are usually about 13cm long.
The Rio Grande Chub has large eyes and an elongated head. They also have a forked tail. They typically have a dark dorsal side, or back. They have a light underside. The colors gradually get lighter as you move to the ventral side. They have two faint black lines along the sides of their body. One these lines is above the fish's lateral line and the other is below. While these fish are breading, the fins, sides, and mouth of the fish will take on a yellowish color. Males will express brighter colors than females during this period.
More detailed identification can be achieved by counting the number of scales that make up this fish's lateral line. The Rio Grade Chub will have between 51 and 67 scales that create the lateral line.
There are also 8 rays in both the dorsal and anal fin. This fish also has 6 to 10 gill rakers.
Habitat
The Rio Grande Chub can be found in small, flowing bodies of water. Small streams and rivers, headwaters, and flowing pools are this fish's preferred habitat.
They have also been found in small lakes and ponds. Occasionally, the Rio Grade Chub will live in engineered waterways. Examples of this include irrigation ditches, canals, and stock ponds.
The Rio Grande Chub prefers cool, flowing water. They also require cover within their habitat. Undercut banks, overhanging vegetation, in-stream woody material, and in-stream vegetation all provide this fish enough cover for suitable habitat. There is also some evidence that they like areas with a bottom consisting of sand, gravel, cobble, or a combination of the three.
This fish needs gravel and cobble areas to spawn. They can be found between 7580 and 8400 feet in elevation and between 12 and 69 inches in the water column.
Diet
The Rio Grande Chub is characterized by some as a mid-water carnivore. This fish preys on zooplankton, insects, crustaceans, and juvenile fish.
The Rio Grande Chub also exhibits some omnivore behavior. They will eat limited vegetation and some amount of detritus.
Beyond this, very little is known about the feeding habits of this fish. Its specific food preferences are not known. Likewise, the impacts of habitat, migration, and competition on this fish's feeding have not been studied. One study did show that Rio Grande Chub have a higher success rate when they prey on larvae with smaller cases.
This fish evolved alongside the Rio Grande Cutthroat trout and the Rio Grande sucker. It fills a unique tropic position within the ecosystems it is found in. There is no evidence that any other fish can fill this position in place of the Rio Grande Chub.
Conservation Concerns
The Rio Grande Chub does not currently have any federal protections or listings under the Endangered Species Act. However, the US Forest Service lists this fish as a sensitive species. It is also listed as a sensitive species with the Bureau of Land Management.
Populations of the Rio Grande Chub have significantly decided from historical levels. At one point, this Chub was the most common fish in the Rio Grande Watershed. It is estimated that overall numbers have declined by 75 percent.
One of the largest factors that has been attributed to the decline of the Rio Grande Chub is the introduction of other non-native fishes.
Brook trout
The brook trout (''Salvelinus fontinalis'') is a species of freshwater fish in the char genus ''Salvelinus'' of the salmon family Salmonidae. It is native to Eastern North America in the United States and Canada, but has been introduced elsewhere ...
and
Brown trout
The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...
were both introduced into the Rio Grande watershed. They replaced the
Rio Grande Cutthroat trout
The Rio Grande cutthroat trout (''Oncorhynchus clarki virginalis''), a member of the family Salmonidae, is found in northern New Mexico and southern Colorado in tributaries of the Rio Grande.
It is one of 14 subspecies of cutthroat trout native ...
as ecosystem's top predator. Both of these species compete with the Rio Grande Chub for resources. They also prey upon the Chub. Other non-natives like
Common Carp
The Eurasian carp or European carp (''Cyprinus carpio''), widely known as the common carp, is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia.Fishbase''Cyprinus carpio'' Linnaeus, 1758/ref>Arkive The ...
and
Northern Pike
The northern pike (''Esox lucius'') is a species of carnivorous fish of the genus '' Esox'' (the pikes). They are typical of brackish and fresh waters of the Northern Hemisphere (''i.e.'' holarctic in distribution). They are known simply as a ...
are also suspected to prey on the Rio Grande Chub at various stages along its life cycle.
Habitat fragmentation and destruction have also reduced Rio Grande Chub numbers. Impoundments such as dams and diversions have fragmented this fish's habitat and interfere with its migration and colonization efforts. Dams prevent genetic exchange between population. Water released from dams also changes the thermal regime of the water the Rio Grande Chub inhabits. This has created colder conditions in the winter and warmer water in the summer then what was historically present.
Some Rio Grande habitat has been destroyed by human manipulations. These include overgrazing in riparian areas, constriction of roads and bridges in areas with highly erodible soil, and bad timer harvest practices.
All of these factors, and many more, change the chemistry and geometry of Rio Grande Chub habitat which negatively impacts the fish.
In Colorado, the Rio Grande Chub is listed as a species of concern. It is designated a tier 1 species of greatest conservation needed.
Population declines in Colorado can be attributed to habitat destruction and the introduction of non-native species. Many of the populations in Colorado are isolated which increases the likelihood of further decline.
Conservation efforts for the Rio Grande Chub are focused on many areas. Conservation requires further study on this fish's habitat requirements and life history.
Some efforts are focused on maintaining natural streamflow conditions. This includes reducing the amount of water diverted from Rio Grande Chub habitat and limiting the amount sediment in waterways. Other efforts focus on protecting the vegetation that is critical for Rio Grande Chub habitat. New regulations are also intended to limit the amount of livestock grazing in riparian areas and prohibit bad land use practices that increase erosion and the sediment load in the water.
References
{{Taxonbar, from=Q6398177
Chubs (fish)
Freshwater fish of the United States
Gila (fish)
Fish described in 1872
Taxa named by Edward Drinker Cope