| Abstract: | Assemblage structure was examined by population monitoring in three reaches of Smoke Creek with different environments. Two hundred ninety-seven population estimates were made during 11 seasonal samples from 1985- 1988. Headwater samples were made near a spring where environmental fluctuation was minimal, mid-basin and low basin samples were in harsh environments. Four native species and two introduced fish species were found. Population and biomass densities fluctuated most in the lower basin where fluctuations of more than three orders of magnitude followed a winter flood. Differences between population and biomass densities of total populations and adult and juvenile segments of the populations were significant for years, species, habitat type, and reach. Differences were not significant between seasons, due to wide within-season variation during the study. Difference between reaches in spatial and temporal variation within were significant for population and biomass densities of the total population, and adults and juveniles. Growth rates of cohorts spawned in 1986 and 1987 differed between stream reach and species. The length of speckled dace cohorts (Rhinichthys osculus) was usually greatest near the terminus; however, differences between growth in the headwaters and near the terminus were not significant. Mean length of the 1986 Tahoe sucker (Catostomus tahoensis) cohort near the headwaters exceeded its length near the terminus, however, mean length of the 1987 cohort near the terminus exceeded that observed in the headwaters. Differences between sucker growth rates in the two reaches were nonsignificant and significant for the 1986 and 1987 cohorts, respectively. In situ observations of fishes in the headwaters of Smoke Creek indicated that adults and juveniles of each species segregate habitat according to the niche diversification hypothesis. Field experiments involving manipulation of density and species composition of the three species most abundant in Smoke Creek led to the conclusion that speckled dace and Tahoe sucker microhabitat use was most affected by intraspecific density, and minimally by competition. Lahontan redsides (Richardsonius egregius) were most affected by intraspecific density and by competition with the complete assemblage. The Smoke Creek fish assemblage is affected by resource availability as affected by density and competition, seasonal variation, and environmental variability. Note: dissertation citations and abstracts contained here are published with permission of ProQuest Information and Learning. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by addressing your request to UMI® Dissertation Services, 300 North Zeeb Road, Ann Arbor, MI 48106-1346 USA. Telephone (734) 761-7400; Web-page: wwwlib.umi.com/dissertations. |
