Minnow
 
   
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The Devils River minnow (Dionda diaboli) is a highly imperiled freshwater fish that inhabits small spring-fed streams with fast flowing water. The Devils River minnow survives in only three tributaries to the Rio Grande in southern Texas and one drainage in northern Mexico. Once one of the most abundant of native fishes in southern Texas, the minnow is now one of the least abundant fish species. Within the U.S., the minnow currently inhabits only the middle Devils River, Pinto Creek, and San Felipe Creek tributaries to the Rio Grande. The minnow may also persist in the Río Salado in Chihuahua, Mexico.

Surveys have demonstrated a massive decline in population and reduction in range of the Devils River minnow due to habitat loss from dam construction, spring de-watering, and other stream modifications. Introductions of non-native fish such as smallmouth bass and armored catfish have contributed to collapse of the minnow population in Devils River, through direct predation, competition for food and destruction of suitable habitat. Imminent threats to the minnow include degradation of water quality from reduced stream flow and stream channel modifications from irrigation, bank stabilization and flood control projects. These changes, in concert with drought, have degraded native fish habitat.

The Devils River minnow has been completely eliminated from several areas in southern Texas, including the lower portions of the Devils River due to construction of Amistad Reservoir, the Upper Devils River due to lack of stream flows, and Las Moras Creek due to damming in the area. The minnow has also been extirpated from the Río San Carlos in Mexico.

In October of 2005 the Center, Forest Guardians, and Save Our Springs Alliance filed a lawsuit against the U. S. Fish and Wildlife Service seeking increased protection under the Endangered Species Act for the Devils River minnow. The lawsuit challenges the designation of the minnow as a threatened rather than an endangered species and the FWS failure to designate critical habitat for the species. (View the press release about the lawsuit).

Although first proposed for endangered listing under the Endangered Species Act in 1978, the Devils River minnow was not listed until 1999, as a threatened species. (View the final rule listing the minnow as a threatened species). The minnow population has decreased immensely and suffered a significant range reduction since the species was first collected in 1951. The lawsuit alleges that the FWS violated the Endangered Species Act by failing to use the best available science in designating the minnow as threatened rather than endangered and by refusing to designate critical habitat for the minnow, falsely asserting it would not be beneficial to the species.

The FWS ignored the fact that critical habitat provides additional protections beyond listing and is an important tool for recovering endangered species. Critical habitat provides protection of areas not currently occupied by the species and protects critical habitat from adverse modification. A peer-reviewed study in the April 2005 issue of BioScience, The Effectiveness of the Endangered Species Act: A Quantitative Analysis, concludes that species with critical habitat designated for two or more years are more than twice as likely to have improving population trends than species without.

The FWS approved a final recovery plan for the Devils River Minnow in September of 2005, which relies exclusively on voluntary recommendations. Conservation groups believe the plan is insufficient not only for recovery, but to prevent the minnow’s extinction.

The Devils River minnow is part of a unique fish fauna in the area where the Chihuahuan Desert, Edwards Plateau, and South Texas Brush eco-regions join. Fishes in this area have been heavily impacted by human water use and introduced species, and half of the native fishes of the Chihuahuan Desert in Texas and Mexico are considered imperiled, with four species already having gone extinct. In 2003, the Rio Grande was rated by American Rivers as one of the most endangered rivers in the U.S.

graphic
Santa Barbara Museum of Natural History
October 6, 2005
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