Disperse and Dispatch: Increasing and maintaining native fish populations in the Pahranagat Valley

Authors: Kevin Guadalupe, Brian M. Hobbs

Year: 2010 (xlii)

Abstract

A snorkel census of the last remaining occupied Pahranagat roundtail chub, Gila robusta jordani, habitat in the Pahranagat Valley was completely surveyed in June 2010. This was only the third complete survey since 2001. Only two fish were counted. The only hopeful sign was that these fish were young adults, likely in the 1 to 2 year old range, indicating successful reproduction must have occurred in the recent past. Fortunately, the refuge population of chub at Key Pittman Wildlife Management Area is doing very well and could serve as a seed population in the future. Approximately 90 Pahranagat Valley speckled dace, Rhinichthys osculus velifer, whose range has decreased significantly due to habitat loss over the past 20 years, were transferred to Maynard Spring just south of the Pahranagat National Wildlife Refuge (PNWR). Pahranagat speckled dace now occur in only three springs in the valley. During a February 2010 snorkel survey of Ash Springs, 730 White River springfish, Crenichthys baileyi baileyi, were counted. The population was locally robust but significant portions of habitat were dominated by shortfin mollies, Poecilia mexicana, and convict cichlids, Amatitlania nigrofasciata. A blue tilapia, Oreochromis aureus, was observed during this survey. This was the first and only tilapia ever observed in the Ash Springs outflow and was later removed with extreme prejudice using a spear. Removal of nonnatives from Hiko and Crystal springs has been ongoing since 2002. Over the years we have learned that the red swamp crayfish, Procambarus clarkii, that inhabit these two systems are likely having the most impact on the Hiko White River springfish, C. b. grandis, population. In 2009 we began to target the crayfish with traps that had larger mesh to allow springfish to escape. This feature allows us to set these traps for long periods, including overnight when the crayfish are most active, without undue harm to springfish. Thousands of crayfish have been removed and it appears that the C. b. grandis population in Hiko Spring may be responding positively. Future efforts include restocking G. r. jordani into historic habitats on private land and the PNWR, continuing efforts to expand the number of speckled dace populations and removing nonnative species throughout Pahranagat Valley.