Relict Dace conservation in Ruby Valley, Nevada: spring restoration, genetic status, and reintroduction efforts

Authors: Susan G.* Mortenson, Chad R. Gourley, Jeff D. Petersen, Dennis K. Shiozawa

Year: 2015 (xlvii)

Abstract

Relict dace, Relictus solitarius, are small minnows that evolved in isolated basins of northeastern Nevada. Following the recession of Pleistocene pluvial lakes they have been confined to desert springs and streams. This species is considered Á¢â‚¬Å“Near ThreatenedÁ¢â‚¬Â by NatureServe due to interactions with non-native species and habitat dewatering, and the US Fish and Wildlife Service (FWS) is currently evaluating R. solitarius for listing under the Endangered Species Act. Relict dace are the only known fish native to Ruby Valley, and their abundance has declined due to fisheries management practices, especially the introduction of largemouth bass (Micropterus salmoides), signal crayfish (Pacifastacus leniusculus), and speckled dace (Rhinichthys osculus). The FWS initiated a collaborative project with Nevada Department of Wildlife, Brigham Young University, and Otis Bay Ecological Consultants to: 1) examine the genetics of relict dace in and near the Ruby Valley National Wildlife Refuge (NWR) to determine where pure strains of relict dace (i.e., populations not hybridized with speckled dace) existed, 2) investigate habitat characteristics of spring pools in the Ruby Valley NWR, 3) design and implement plans to restore or create ponds isolated from introduced species, 4) translocate individuals from pure strain populations to restored ponds, and 5) monitor translocated relict dace populations. Genetic analyses revealed that five of the sixteen springs in Ruby Valley contained pure relict dace. Hybridization of relict and speckled dace was documented at one spring beyond the F1 generation, indicating that viable offspring can result from interbreeding. Ponds in Ruby Valley NWR that could be physically isolated from introduced species were identified. In 2011 five new ponds were constructed and five existing ponds were restored to create shallow water habitat for the relict dace. Water control structures were designed and installed to prevent colonization of these ponds by introduced species, and chemical treatments were applied to remove introduced species from existing ponds. In 2012 and 2013 relict dace were captured from three ponds that contained pure relict dace, and these relict dace were reintroduced to three of the restored ponds. Surveys in 2014 revealed that all three ponds contained relict dace, and reproduction was documented in one of the ponds. Additional surveys are planned in October 2015. Relict dace may be reintroduced to two more ponds if absence of speckled dace is verified. These efforts will continue to ensure persistence of relict dace in Ruby Valley.