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Pahrump poolfish

The Pahrump poolfish (Empetrichthys latos) is the only remaining taxon in the Empetrichthys genus [1]. The Ash Meadows killifish (Empetrichthys merriami) became extinct in the late 1940’s. The two other E. latos subspecies (E. l. concavus = Raycraft Ranch springfish and E. 1. pahrump = Pahrump Ranch killfish) were driven extinct by water pumping in the mid-1950s and 1958 respectively [1]. The Pahrump poolfish is now the only fish native to the Pahrump Valley in southern Nye County, Nevada. It is endemic to Manse Spring, but was removed from this habitat when it became apparent that the spring would go dry due to groundwater pumping [2].

Los Latos Pool. This site along the Colorado River was used as a reintroduction site in 1970, but the population was lost during flooding in the 1970s and never replenished [3].

Corn Creek Springs. This site on the U.S. Fish and Wildlife Service’s Desert National Wildlife Range north of Las Vegas received 29 pool fish from Manse Spring in 1971 [3]. The population thrived until the illegal introduction of bullfrogs and crayfish occurred in the late 1990s. The population was reduced to three fish in 1998 and was not found thereafter. In 2003, 120 fish were transplanted to two new secure, but small tanks. The population was estimated at 141 fish in 2004. The Nevada Department of Wildlife opined in 2005 that the tanks would never be capable of sustaining the thousands of fish which formerly inhabited the springs. It recommends eventually reintroducing the poolfish to the springs.

Shoshone Ponds. In 1970 the Bureau of Land Management designated the Shoshone Ponds and 1,240 surrounding acres as the Shoshone Ponds Natural Area [3]. Sixteen fish from either Corn Creek or Manse Spring were transplanted in 1972, but were extirpated in 1974 due to vandalism. Fifty fish were transplanted from Corn Creek in 1976 and the population has experienced only natural population fluctuations from the 1980s to the early 2000. In 2003, however, the population level dropped to below 1,000 fish for unknown reasons.

Spring Mountains Ranch State Park. In 1983 exotic fish were eradicated from pools at Spring Mountains Ranch State Park and 426 poolfish were introduced from Corn Creek [3]. The property has consistently been the largest and most stable of the poolfish populations. Over 500 fish were present between 1985 and 1993. Population estimates were 24,800 fish in 1989, 16,775 in 2003 and 29,876 in 2004.

The 1980 U.S. Fish and Wildlife Service recovery plan required the establishment of three populations >= 500 fish for three consecutive years in order to downlist the species to threatened [4]. Delisting can occur if the populations remain at 500 adults for another three years after downlisting [4]. The habitat of the three populations must also be secured [4].

In 1993 the U.S. Fish and Wildlife Service published a downlisting proposal because the species had over 500 individuals at all three sites from at least 1986 through 1992 [4]. From 1988 to 1992 the populations at each site contained “far greater than 500 individuals" [4]. The habitat was deemed sufficiently secure because the U.S. Fish and Wildlife Service had applied for vested water rights at Corn Creek Springs, the Nevada Department of Wildlife had State appropriative water rights at Shoshone Ponds, and the Nevada Division of State Parks has appropriated water rights for Sandstone Spring, the water source for the Spring Mountain Ranch irrigation impoundment [4]. The temporary loss of Corn Creek and the 2003 population decline at Shoshone Ponds caused the Wildlife Service to withdraw the proposed rule in 2004 [1].

[1] USFWS. 2004. Withdrawal of proposed rule to reclassify the Pahrump Poolfish (Empetrichthys latos) from endangered to threatened status. U.S. Fish and Wildlife Service, April 2, 2004 (69 FR 173830
[2] U.S. Geological Survey. Pahrump Poolfish: Status of Listed Species and Recovery Plan Development. Website <http://www.npwrc.usgs.gov/resource/distr/others/recoprog/states/species/empelato.htm> accessed May, 2006.
[3] Nevada Department of Wildlife. 2005. Pahrump poolfish monitoring and recovery activities. Draft report provided by Jon C. Sjöberg, Nevada Department of Wildlife, Las Vegas Nevada, August 21, 2005.
[4] USFWS. 1993. Proposed reclassification of the Pahrump Poolfish (Empetrichthys latos latos) from endangered to threatened status. U.S. Fish and Wildlife Service, September 22, 1993 (58 FR 49279).

Banner photo © Phillip Colla