GENETIC-VARIABILITY IN PRE-BOTTLENECK AND POST-BOTTLENECK SEGMENTS OFTHE CUI-UI (OSTEICHTHYS, CHASMISTES CUJUS) POPULATION OF PYRAMID LAKE, NEVADA

Cui-ui (Chasmistes cujus), an endangered catostomid endemic to Pyramid Lake, NV, recently experienced a 19-year hiatus in reproduction due t o low water levels in its primary spawning stream, the Truckee River. The effects of this bottleneck on the genetic variability of the cui-u i population were examined using starch-gel electrophoresis. Nine 1950 (pre-bottleneck) and four post-bottleneck (1969 and 1977) age-class f ish were analyzed at 55 presumptive allozyme loci. Allozyme data were also available for 31 additional post-bottleneck fish. Pre-bottleneck cui-ui were polymorphic at two loci and exhibited an estimated heteroz ygosity of 0.0081, and post-bottleneck fish were poly morphic at four loci and exhibited heterozygosity estimated at 0.0036. One allele was detected in the pre-bottleneck fish but not in post-bottleneck cui-ui at the IDH-2 locus. Thus, post-bottleneck cui-ui appear reduced in ge netic variation as compared to pre-bottleneck fish. Conservation recom mendations for the genetic management of the Pyramid Lake cui-ui popul ation are discussed in light of these results.