Gila pandora

This species hybridizes with Rhinichthys cataractae (may be due to breeding-season crowding caused by drought and/or withdrawals of water for irrigation). Morphological variation among populations in Canadian River, Pecos River, and Rio Grande are believed to represent ecophenotypic variation (Sublette et al. 1990).

Small range in New Mexico, western Texas, and south-central Colorado; large decline in distribution and abundance; locally fairly common; primary threats are stream degradation and effects of non-native species.

Formerly this species was widespread in creeks of the upper Rio Grande and Pecos watersheds in New Mexico and the Rio Grande and San Luis basin in southern Colorado, with an isolated population in the Davis Mountains, Texas (Little Aguja Creek [Nations Canyon Creek], Pecos River system, Jeff Davis County) (Sublette et al. 1990, Zuckerman and Langlois 1990, Calamusso and Rinne 1996, Bestgen et al. 2003, Rees et al. 2005, Hubbs et al. 2008). Now the range is reduced in the Pecos system, and likely the species has been extirpated from the mainstem Rio Grande and is now only found in tributary streams (Rees et al. 2005). A population in the headwaters of the Canadian River (Red River drainage), New Mexico, may be introduced or possibly native (Sublette et al. 1990); Page and Burr (2011) regarded it as introduced. An isolated, introduced population occurs in Dome Lake on the Gunnison National Forest, Colorado (Rees et al. 2005). Elevational range extends to at least 3,470 meters (Zuckerman and Langlois 1990).

Several small subpopulations exist in Colorado, and many small subpopulations occur in New Mexico (Zuckerman and Langlois 1990, Calamusso and Rinne 1996, Bestgen et al. 2003, Rees et al. 2005).

Water diversion projects have resulted in flow regime changes in both tributary and mainstem rivers and streams (Rees et al. 2005). Construction of diversion dams and reservoirs has degraded and fragmented habitats and caused passage barriers (Rees et al. 2005). The introduction of non-native species (e.g., brown trout, brook trout, northern pike, common carp, white sucker) has increased predation and competition (Rees et al. 2005). Land use changes and local development (e.g., road building, timber harvesting, mining) and excessive grazing in riparian zones have degraded natural stream ecosystem function (Bestgen et al. 2003, Rees et al. 2005). Stream bank degradation can result in increased sedimentation, and additional sediment loads can fill pool and run habitats, cover benthic substrate, and smother benthic organisms (Rees et al. 2005). The change in sediment load also can result in streams becoming wider and shallower and result in higher than normal water temperatures (Rees et al. 2005).

Aquatic habitats of both the Rio Grande drainage and San Luis Closed Basin have been degraded by dewatering, sedimentation, fish culture and stocking, fishing, transbasin diversions, irrigation, input of domestic sewage effluent, stream channelization, and input of fertilizers and pesticides (Zuckerman and Langlois 1990).

Primary threats are stream dewatering and habitat modification due to channelization (New Mexico Department of Game and Fish 1996).

The potential is high for future declines in distribution and abundance; isolated populations are more susceptible to catastrophic events because recolonization from nearby populations is unlikely (Rees et al. 2005).

Jelks et al. (2008) categorized this species as Vulnerable due to (1) present or threatened destruction, modification, or reduction of habitat or range; (2) disease or parasitism; and (3) other natural or anthropogenic factors that affect a taxon's existence, including impacts of nonindigenous organisms, hybridization, competition, and/or predation.