The Rio Grande Chub (Gila pandora) is a cyprinid fish endemic to the United States. It inhabits the upper Rio Grande and Pecos River systems in Colorado, New Mexico and Texas. 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 (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 and Brown trout were both introduced into the Rio Grande watershed. They replaced the Rio Grande Cutthroat trout 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 and Northern Pike are also suspected to prey on the Rio Grande Chub at various stages along its life cycle.