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Moapa dace

The Moapa dace (Moapa coriacea) is endemic to the upper Muddy River in southern Nevada where it occurs in warm springs, spring outflows, and the river mainstem [2]. It was "rather common" in about 10 miles of the upper Muddy River and in 25 warm springs when discovered in 1938. As of 1959 it was still considered common, but declined significantly after the introduction of the shortfin molly (Poecilia mexicana) in 1963. It is unclear whether the molly or habitat degradation was the principle cause of decline.

By 1969 the species had declined to 500-1,000 individuals, and it reached a low point in 1977 only "several hundred" remained. Significant conservation efforts began in 1979 when the U.S. Fish and Wildllife Service purchased the 7-12 Resort and established the Moapa National Wildlife Refuge. It was the first refuge established for an endangered fish. As of 2005, over 95% of the species's reproduction occurs within the refuge.

The species improved throughout the 1980s, increasing its distribution from three springs and less than two miles of streams in 1983 to five springs (Apcar, Baldwin, Cardy Lamb, and Muddy Spring on private lands and the Refuge spring system originating in the Moapa Valley National Wildlife Refuge) and 5.9 miles of stream in 1996 [2]. The population reached a high of 4,341 fish in 1994, but a fire in the refuge that year reduced the number by 500. The species was not significantly impacted by the illegal introduction of tilapia into the river system in 1991 because the two fish were largely separated, but it went into a tailspin when a hydropower barrier was removed allowing the tilapia to move upstream[1, 3, 4, 5]. By 1997 only 1,500 dace remained. The population hovered around 1,000 from 1997 to 2003, but increased to 1,296 in 2005 due to extensive habitat restoration, tilapia removal, and construction of fish barriers.

[1] Desert Fishes Council. 1992-2003. Proceedings of the Desert Fishes Council Annual Symposium, 1992-2003
[2] U.S. Fish and Wildlife Service. 1996. Recovery Plan for the Rare Aquatic Species of the Muddy River Ecosystem. U.S. Fish and Wildlife Service, Portland, OR.
[3] Cook, A.E., C.T. Martinez, J.S. Sjoberg, S.C. Goodchild, G.G. Scoppettone, G. Clemmer, J.E. Heinrich and J. French. 2002. Nevada 2002 Area Report. In D.A. Hendrickson and L.T. Findley (eds.), Proceedings of the Desert Fishes Council, VOLUME XXXIV, 2002 Annual Symposium.
[4] Stein, J.R., J.E. Heinrich, J.F. Sjoberg, B.M. Hobbs and D. St. George. 2000. Native fish and amphibian management in southern Nevada. In In D.A. Hendrickson and L.T. Findley (eds.), Proceedings of the Desert Fishes Council, VOLUME XXXIi, 2000 Annual Symposium.
[5] Miskow, E., G. Clemmer, S. Goodchild, J. Heinrich, B. Hobbs, J. Sjoberg, K. Tisdale, and G. Webber. 2005. Nevada 2005 Area Report. In D.A. Hendrickson and L.T. Findley (eds.), Proceedings of the Desert Fishes Council, 2005 Annual Symposium.

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