Date of Award

2015

Document Type

Thesis

Degree Name

Master of Science (MS) in Biology

Department

Biology

Abstract

"I conducted a three month study, between June and August, in 2015 of Redband Trout (Oncorhynchus mykiss var. gairdneri) and Smallmouth Bass (Micropterus dolomieu) in the upper Spokane River in Washington, from the border between Washington and Idaho (rkm 154.5) to Harvard Road (rkm 149.2). The primary goals of the project were to: (1) determine the abundance and density of Redband Trout and Smallmouth Bass in the Starr Road area, as well as two reference sites, prior to possible habitat manipulation, (2) estimate the Smallmouth Bass population and density between the Washington/Idaho Stateline and Harvard Road, and (3) determine the rate of piscivory on Redband Trout by Smallmouth Bass. Day and night snorkel surveys were conducted to determine abundance and density at the Starr Road experimental site, and two additional references sites. Only two adult and three juvenile Redband Trout were at any of the sites during the study, therefore no statistical testing was done. There were significantly more Smallmouth Bass were observed at Starr Road (n=2692) than either reference site 1 (n=864) and site 3 (n=901) (p = < 0.001, 95% C.I. = 36.002/38.828). The Smallmouth Bass population between the Washington/Idaho Stateline and Harvard Road was estimated by mark/recapture techniques. Fish, collected by raft electrofishing and angling, >̲ 150mm were tagged with a Floy tag and fish <̲ 150mm were tagged with elastomer. Fish were also given right pelvic fin clip if captured by angling and a left pelvic fin clip if captured by electroshocking. I used an open population model POPAN in the mark program to conduct estimates for both Smallmouth Bass >̲ 150mm TL and Smallmouth Bass TL and >̲ 200mm TL. Populations estimates (± SE; 95% CI; AIC value) were 1,645 (SE=287; 95% C.I. = 1,171-2,310, AIC=429) Smallmouth Bass >̲ 150mm and 1,307 (SE = 218; 95% C.l. = 945-1807, AIC=402) Smallmouth Bass >̲ 200mm TL. Density of Smallmouth Bass >̲ 150mm TL and >̲ 200mm TL were 284 fish/km and 225 fish/km, respectively. In a previous study conducted by the Washington Department of Fish and Wildlife in (2009), the Smallmouth Bass population >̲ 200mm TL (± 95% CI) between the Stateline, of Washington and Idaho, to McMillian Road was estimated at 902 (524-1691) and had a density of 100 fish/km. The density of Smallmouth Bass >̲ 200mm TL increased 125 percent between 2009 and 2015. A diet survey was conducted to determine the amount of predation occurring on Redband Trout by Smallmouth Bass. No predation of Redband Trout by Smallmouth Bass was observed during the study, though only 5 young-of-the-year Redband Trout were seen during the entirety of the study. Smallmouth Bass in the study area consumed substantial numbers of non-salmonid fish, which comprised 33 percent of their diet by weight"--Leaves iv-v.

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