|Scientific Name:||Plagopterus argentissimus|
|Species Authority:||Cope, 1874|
|Red List Category & Criteria:||Critically Endangered B1ab(i,ii,iii,v) ver 3.1|
|Reviewer/s:||Smith, K. & Darwall, W.R.T.|
|Facilitator/s:||Hammerson, G.A. & Ormes, M.|
This species is listed as Critically Endangered because its extent of occurrence is less than 100 sq km, number of locations is one, and distribution, abundance, and habitat extent and quality are declining.
|Range Description:||This species' historical range included the Colorado and Gila river basins in Arizona, Nevada, and Utah, including at least the Colorado River from Yuma upstream into the Virgin River in Nevada and Utah, and the Gila River from Yuma to the confluence of the Salt River. No barriers or habitat considerations would have limited the species to this specific area, so it is likely that the historical range extended farther upstream in the Verde, Salt, and Gila rivers in Arizona (USFWS 2000).
Preliminary sampling results collected in 2007 indicated that the wild Woundfin population was functionally extirpated throughout its designated critical habitat (140 stream-kilometres along the Virgin River) (USFWS 2008). Hatchery-raised Woundfin have been stocked in the upper Virgin River, and additional releases are planned in the future.
In 1972, Woundfin were transplanted into four locations in the Gila River system, but populations were not established (USFWS 2008). In 1985, streams in the Gila River drainage (Hassayampa, Verde, San Francisco, and Gila rivers, and Tonto Creek) were identified as reintroduction sites, and the Gila River drainage was designated as a nonessential experimental population. Reintroduction efforts in the Gila River drainage in Arizona are underway (USFWS 2008).
|Range Map:||Click here to open the map viewer and explore range.|
This species is represented by very few occurrences (subpopulations) (only one if the Virgin River is regarded as a single metapopulation).
Total adult population size is unknown.
Surveys in the early 1970s found that the Woundfin was the most common native species, comprising about half (5,000 of 10,822) of the native fish collected (Cross 1978). It has declined greatly since then, with increases in the range and abundance of the red shiner. The species now occupies not more than 12 percent of the estimated historical range (USFWS 2000).
Over the past 30 years, Woundfin have generally declined throughout their occupied range and critical habitat. They have been extirpated from the Lower Virgin River (i.e., from Beaver Dam Wash, perhaps from the Utah / Arizona State line, downstream to Lake Mead). Populations in Utah, particularly those upstream of the influence of red shiner (i.e., upstream of the Washington Fields Diversion), have persisted better than anywhere else (USFWS 2008).
Distribution and abundance have declined over the past 10 years or three generations (three generations is roughly 10 years). In the past 20 years, Woundfin have been eliminated from at least 56 kilometers of designated critical habitat in the lower Virgin River, and abundance has declined to precariously low levels elsewhere (USFWS 2008).
|Habitat and Ecology:||Habitat includes seasonally swift, warm, highly turbid, small to medium rivers, with constantly shifting substrates (Lee et al. 1980, Matthews and Moseley 1990, Page and Burr 2011). Adults and juveniles inhabit runs and quiet waters adjacent to riffles with sand and sand/gravel substrates (USFWS 2000). Adults are generally found in habitats with water depths of 0.15–0.43 m and velocities of 0.24–0.49 m per second, whereas juveniles select areas with slower and deeper water, and larvae are found in backwaters and stream margins which are often associated with growths of filamentous algae (USFWS 2000). Spawning occurs in swifter flowing water over beds of cobble or gravel (Matthews and Moseley 1990).|
The Virgin River system has been negatively affected by agricultural and energy development, and the decline of the Woundfin has been due in part to habitat loss, fragmentation, and degradation caused by associated dams, reservoirs, and water diversion. Completion of Quail Creek Reservoir in Utah in 1985 was followed by a substantial decrease in the abundance and area of occupancy of the Woundfin.
Changes to flow patterns caused by dams and diversions have facilitated movement of red shiners upstream in the Virgin River (USFWS 1994). The non-native red shiner largely has replaced the Woundfin and has introduced the Asian tapeworm, which now parasitizes many of the remaining Woundfin (Heckmann et al 1986). Maintenance of a 26-kilometer red-shiner-free zone has required monumental management efforts, and the threat of red shiner expansion remains as prevalent today as it was in the late 1980s when red shiners became established in the upper river (USFWS 2008).
The Woundfin inhabits one of the fastest-growing parts of Utah, and associated extensive water development is an ongoing threat (Minckley and Deacon 1991).
Failure of a dike at Quail Creek Reservoir and a resulting flood of relatively enormous magnitude detrimentally affected the Virgin River Woundfin habitat (Hendrickson and Brooks 1991).
Primary threats are competition and predation from non-native species (primarily Red Shiner) and degraded habitat conditions (reduced flow/high temperatures) (USFWS 2008). Causes for the most recent decline in Woundfin numbers was attributed to the following suite of environmental conditions: continued drought with summer temperatures exceeding behavioural thermal maximum and critical thermal maximum; runoff from burned portions of the drainage; and the input of sediment from behind the Quail Creek Diversion Dam (USFWS 2008).
Actions Needed (USFWS 1994):
|Citation:||NatureServe 2013. Plagopterus argentissimus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 16 April 2014.|
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