Resident bull trout (Salvelinus confluentus) may be particularly vulnerable to human related
disturbance, however very few studies have focused on resident bull trout populations. The
abundance of bull trout is one measure of the strength and potential for persistence of a
population. Habitat characteristics may influence resident bull trout abundance to differing
degrees and by varying means at multiple spatial scales. We used day and night snorkel
counts to assess relative bull trout abundance. A modification of the Forest Service R1/R4
Fish and Fish Habitat Inventory was used to assess habitat characteristics associated with
resident bull trout. Logistic and multiple linear regression were used to assess the
relationships between resident bull trout abundance and habitat characteristics at the patch (1
to 5 km), reach (0.5 to 1 km) and habitat unit (1 to 100 m) scales. Site categorical variables
were used along with quantitative habitat variables to explain among-site and across-site
variation in the data. The significance of both quantitative habitat variables and categorical
site variables at various spatial scales suggest that relationships between bull trout abundance
and habitat characteristics are complex and in part dependent on scale. The characteristics of
individual habitat units explained little of the variation in bull trout presence/absence (logistic
regression; Somers' D=0.44) and density (multiple linear regression; adjusted R��=0.08) in
habitat units, however there were habitat characteristics that were significantly (P���0.05)
correlated to bull trout presence/absence and density in habitat units. The relationships
between habitat characteristics and bull trout presence/absence and density varied between
habitat unit types. There was a strong quadratic relationship between bull trout abundance and
mean summer water temperature at the reach (P=0.004) and patch scales (P=0.001). The
mean temperature of patches appears to explain some of the variation in bull trout density at
smaller spatial scales, such as reaches and habitat units. An appreciation of the complex
nature of scale dependent interactions between bull trout abundance and habitat characteristics
may help resource managers make wiser decisions regarding conservation of resident bull
trout populations. / Graduation date: 2000
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33336 |
| Date | 07 March 2000 |
| Creators | Zurstadt, Caleb Frederick |
| Contributors | Liss, William J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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