Graduation Date

Fall 2020

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Fisheries

Committee Chair Name

Darren M. Ward

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Bret C. Harvey

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Mark Henderson

Third Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Fisheries

Abstract

Removal of four major dams on the Klamath River is scheduled to begin in 2023, restoring access to greater than 50 km of historic mainstem habitat for coho salmon. However, mainstem habitat may not be suitable for juvenile coho salmon due to elevated water temperatures and high concentrations of infectious myxospores in the summer and fast water velocities in the winter. Small, cooler tributaries can provide essential habitat for escape from deleterious conditions in the mainstem Klamath River. I used temperature and other physical features of six tributaries to the Klamath River above Iron Gate Dam to assess their capacity to support juvenile coho salmon following dam removal. I applied the Habitat Limiting Factors and Intrinsic Potential models to tributaries above Iron Gate Dam to estimate potential capacity. I also developed an occupancy model using data from reference tributaries below the dam and from other nearby watersheds to estimate the potential distribution of juvenile coho salmon in tributaries above Iron Gate Dam. I found that the six newly accessible tributary streams will provide greater than 26 km of accessible rearing habitat. Most streams had summer temperature suitable for coho salmon, with maximum weekly maximum and maximum weekly average temperatures ranging from 13.2 °C to 24.0°C and 12.0 °C to 20.7 °C respectively. The Habitat Limit Factors model estimated that the streams could support up to 105,000 juvenile coho salmon in the summer, with most of this capacity (66,300 individuals) in Spencer Creek (note that predicted capacity is not a prediction of actual production following dam removal). Four out of the six streams exhibited high intrinsic potential, particularly near their confluences with the Klamath River. In reference streams, coho salmon occupancy ranged from 0.41-0.44 of available habitat. I found that the probability of summertime occupancy by juvenile coho salmon was positively correlated with percent instream cover, surface area, and nearby coho salmon hatchery production. Applying these relationships to the study streams, Scotch, Jenny, Fall, Shovel, and Spencer creeks exhibited 0.48, 0.50, 0.53, 0.46, and 0.61 mean occupancy probability respectively. I also found that Scotch, Jenny, Fall, Shovel, and Spencer creeks contained 26%, 2%, 7%, 2%, and 46% by surface area of suitable spawning gravels for adult coho salmon. Based on model predictions and a large quantity of suitable habitat for coho salmon habitat, Spencer Creek should be prioritized for restoration and protection. While Spencer Creek contains a large quantity of suitable habitat for coho salmon, I identified limited spawning and rearing habitat in Jenny, Fall, and Shovel creeks suggesting a need for habitat restoration.

Citation Style

APA

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