|Scientific Name:||Dionda diaboli|
|Species Authority:||Hubbs & Brown, 1957|
|Red List Category & Criteria:||Endangered B1ab(ii,iii,iv,v)+2ab(ii,iii,iv,v) ver 3.1|
|Reviewer/s:||Smith, K. & Darwall, W.R.T.|
|Facilitator/s:||Hammerson, G.A. & Ormes, M.|
This species is listed as Endangered because its extent of occurrence is less than 5,000 sq km, area of occupancy is less than 500 sq km, the species occurs in not more than five locations, the distribution may be severely fragmented, and the species is probably experiencing declines in habitat quality, population size, and area of occupancy in parts of the historical range. Also, in the United States, the species is vulnerable to declines in habitat quality and to reductions in distribution and abundance due to non-native species
|Range Description:||The Devils River Minnow historically occurred in tributaries to the Rio Grande in Texas and Coahuila, Mexico; it was never recorded in the mainstem Rio Grande or the Rio Conchos drainage (USFWS 1999, 2005). Currently the species is known from three streams in Val Verde and Kinney counties, Texas: Devils River, San Felipe Creek, and Pinto Creek (USFWS 2005, López-Fernández and Winemiller 2005). The Pinto Creek occurrence is represented by a large population that was recently found in previously inaccessible locations in the headwaters of that stream in Kinney County (Garrett et al. 2004). The species is believed to be extirpated from the lower portions of the Devils River (now Amistad Reservoir in Val Verde County) and Las Moras Creek (Kinney County) (USFWS 2005, Hubbs et al. 2008). The current status of the species in Sycamore Creek, Texas, is not known (possibly extirpated; USFWS 2008). The species is apparently now rare or extirpated in the Rio San Carlos and Rio Salado basin, Coahuila, Mexico (Garrett et al. 2004, USFWS 2005). Overall, populations are restricted to small reaches of streams that are disconnected from one another (USFWS 2005).|
Native:Mexico; United States
|Range Map:||Click here to open the map viewer and explore range.|
Known distribution includes not more than about a half dozen extant populations (USFWS 1999, 2005; Garrett et al. 2004).
Total adult population size is unknown but presumably at least several thousand. Some recent collections included hundreds of individuals (see USFWS 2005).
Extent of occurrence, area of occupancy, number of subpopulations, and population size have substantially declined. Extirpation in Las Moras Creek and lower Devils River occurred after the species was discovered in the 1950s. A comprehensive assessment of the distribution of Devils River minnow in Texas in 1989 documented a reduced range and showed the species to be rare compared to past collections (Garrett et al. 1992). Limited information for Mexico suggests that the species has declined in range and abundance since the 1980s (see USFWS 2005).
Devils River Minnow (Dionda diaboli) populations were found to be relatively stable in abundance at various localities throughout their current U.S. range, based on multi-year monitoring studies in the Devils River, San Felipe Creek, and Pinto Creek (Desert Fishes Council 2003 meeting abstracts). However, distribution and abundance in Mexico may be declining, and ongoing threats could cause future declines in the United States.
|Habitat and Ecology:||This species is most abundant in fast-flowing, clear, spring-fed water over gravel. It is a channel inhabitant under normal flow regimes, but may occur in shallow riffles after flooding. In the headwaters of Pinto Creek, it was found in flowing, spring-fed waters over gravel-cobble substrates, usually associated with aquatic macrophytes (Garrett et al. 2004). In San Felipe Creek, López-Fernández and Winemiller (2005) found that Dionda diaboli was restricted to creek habitats and did not occur in the spring outflow channels; in some areas it was most numerous where aquatic macrophytes were scarce or absent, but these areas had abundant overhanging riparian vegetation.|
Ongoing primary threats include: loss of spring and stream flow due to groundwater withdrawals; impacts from nonnative species, mainly Armoured Catfish (this threat has increased since the species was listed under the U.S. Endangered Species Act); degradation of water quality due to pollution; and alterations of stream channel habitats (USFWS 2008).
Primary threats are habitat loss and negative effects of non-native aquatic species (USFWS 2005). The species may have been eliminated from Las Moras Creek as a result of periodic chlorination of the spring outflow for swimming pool maintenance (Garrett et al. 1992) or from drying of the spring in the 1960s (Eckhardt 2004). The range was reduced in the upper Devils River (upstream of Pecan Springs) due to lack of stream flow and in the lower Devils River due to the construction and subsequent filling of Amistad Reservoir (Garrett et al. 2004). Low flows during the last 10 years in Sycamore Creek have jeopardized that population (Garrett et al. 2004 unpubl. data). Drought could exacerbate inadequate instream flows. The future of the population in the headwaters of Pinto Creek might be threatened by reduced spring flows resulting from excessive pumping from the associated aquifer (Garrett et al. 2004). Predation by introduced Smallmouth Bass also may have been involved in the decline. The population in San Felipe Creek in the vicinity of Del Rio, Texas, may be threatened by recently introduced Armoured Catfish (Hypostomus) (López-Fernández and Winemiller 2005). Habitat in Mexico faces significant threats from industrial and agricultural development that have negatively affected streamflows, water quality, and channel characteristics (Contreras-Balderas and Lozano-Vilan 1994). See USFWS (1999, 2005) for further details.
The overall risk of extinction is elevated due to such factors as the small number of fragmented populations in relative close proximity, the small fluctuating population sizes, and the fish's short life span (see USFWS 2005).
Conservation measures needed include (USFWS 2005): population monitoring throughout the current range; reestablishment in Las Moras Creek, if scientifically feasible; determination of the status of populations in the Rio Salado drainage in Mexico; maintenance of adequate flows in streams supporting Devils River minnow, including Las Moras Creek (if reestablishment is feasible); protection of surface water quality, including the protection of the quality of groundwater sources of surface water flows, throughout the range, particularly in urban areas such as the cities of Del Rio and Brackettville; and reduction or elimination of deleterious effects of non-native species. Captive propagation will probably be needed for the foreseeable future (USFWS 2005). Public relations efforts should be undertaken to discourage people from introducing aquarium fishes into the San Felipe Creek system (López-Fernández and Winemiller 2005).
The primary focus of the recovery strategy for the Devil's River Minnow is the protection of naturally functioning spring and stream ecosystems within its current and potentially restorable historic range (USFWS 2005).
|Citation:||NatureServe 2013. Dionda diaboli. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 12 March 2014.|
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