Distribution, Abundance, and Coexistence of Two Species of Sucker (Catostomus) in Sagehen Creek, California and Their Status in the Western Lahontan Basin

MASTERS THESIS: In 1982 (the researcher) initiated a study to examine any differences in the distribution and abundance between mountain and Tahoe sucker and to determine how these two similar species coexist in Sagehen Creek. Early in the study (she) noticed that the relative abundance of these species had shifted dramatically when compared to earlier reports. IN addition to Sagehen Creek, four nearby streams were surveyed in 1982 to locate both species. At all sites mountain sucker were either absent or rare and only 10 individuals were eventually collected. The apparent scarcity of mountain sucker was perplexing; early records had shown mountain sucker were not only present and abundant but were also more numerous than the associated Tahoe sucker at these sites. (She) expanded the study to address the following objectives: 1. To determine if significant shifts in the relative abundance of suckers have occurred in Sagehen Creek since early surveys, 2. To determine if similar shifts have occurred elsewhere, 3. To distinguish differences in the distribution and abundance between the two species of sucker in Sagehen Creek where both species still exist, and 4. To determine how mountain and Tahoe sucker manage to coexist in a relatively small segment of stream.