The Borax Lake chub is a small minnow endemic to Borax Lake and adjacent wetlands in Oregon's Alvord Basin (Williams and Bond 1980). Borax Lake is a natural lake, perched 10 meters above the desert floor on sinter deposits, which is fed almost exclusively by thermal groundwater.

Population abundance estimates obtained in 1986-1996 indicated a fluctuating population ranging from approximately 4,100 and 37,000 fish. Recent estimates have ranged between approximately 8,200 and 25,500 chub (Figure 1). The basis for the Borax Lake chub's listed status was not population size, but the security of a very limited, unique, isolated, and vulnerable habitat. Aging data suggests that the Borax Lake chub population consists primarily of age 1 fish, with few age 2 and older fish present. Because Borax Lake chub are only found in one location and the population is apparently dominated by a single year-class of adults, the species has a high inherent risk of extinction.

Figure 1.  Borax Lake chub population abundance estimates from 1986 through 1997 and from 2005 through 2010.  Horizontal bars represent 95% confidence limits.  In 1986-1990 (solid symbols), only the perimeter of the lake was trapped.  After 1990 (open symbols), the entire lake was trapped.  Estimates are not directly comparable across these time periods.

Numerous recovery measures implemented since listing have improved the conservation status of Borax Lake chub and protection of its habitat. When the species was listed, critical habitat was designated on 259 hectares of land surrounding the lake, including 129 hectares of public lands and two 65-hectare parcels of private land. In 1983, the U.S. Bureau of Land Management designated the public land as an Area of Critical Environmental Concern.  The Nature Conservancy began leasing the private lands in 1983 and purchased them in 1993, bringing the entire critical habitat into public or conservation ownership.  The Nature Conservancy ended water diversion from the lake for irrigation and livestock grazing within the critical habitat. Passage of the Steens Mountain Cooperative Management and Protection Act of 2000 removed the public BLM lands from mineral and geothermal development within a majority of the basin. In addition, detailed studies of the chub and theri habitat have added substantially to our knowledge of basic Borax chub biology and the Borax Lake ecosystem. However, three primary threats remain.  These include the threat to the fragile lake shoreline, wetlands, and soils from a recent increase in recreational use around the lake (particularly off-road vehicle usage), the threat of introduction of nonnative species, and potential negative impacts to the aquifer from geothermal groundwater withdrawal if groundwater pumping were to occur on private lands outside the protected areas. This potential threat resurfaced in 2009, when Pueblo Valley Geothermal proposed a geothermal enery project on private property within 5 km of Borax Lake.