Date of Award

2014

Document Type

Thesis

Degree Name

Master of Science (MS) in Biology

Department

Biology

Abstract

Wild kokanee in Franklin D. Roosevelt Lake, commonly known as Lake Roosevelt, comprise an essential part of the fishery in Lake Roosevelt. The salmon population in Lake Roosevelt plays a vital role in the local ecosystem, and also is a major source of socioeconomic income for the surrounding areas of eastern Washington. There are many gaps in the managers’ knowledge of this wild population of kokanee in Lake Roosevelt. In 2008 we initiated a four year study to determine 1) the seasonal reservoir use areas by kokanee, 2) monitor the thermal and depth experience of kokanee throughout the year, 3) determine the extent water temperatures effect these movements, 4) monitor the extent reservoir dynamics effect the population, and 5) identify spawning migration patterns. In 2010, we caught and tagged 25 wild, unclipped kokanee during the month of February. These fish were tagged with Vemco V9TP-2x tags that were equipped with temperature and depth sensors. The initial post-surgery survival in 2010 was 68%, therefore, 23 fish were monitored by 25 Vemco VR2w receivers. Kokanee numbers 20 and 21 were never detected during this study, which could have been due to tag failure, or dying in an undetected area of the reservoir. The kokanee primarily used the lower third of the reservoir, with only one fish moving above the confluence of the Spokane River. The Sanpoil River was utilized by 5 fish (22%) during the spring and summer. The average distance traveled by each of the 23 kokanee was 30.0 km over an average of 93.3 days in the fishery. Spring diel vertical migration patterns were noticed in 15 kokanee (65%) in which kokanee were near the surface during dawn and dusk possibly to feed, and then dove down to 15 – 30 m during the daytime hours. Summer diel vertical migration patterns were identified in 2 fish (9%). The summer pattern was a reversal of the spring pattern where kokanee tended to swim near the surface during the daytime hours, and dove down 50 m or more during the nighttime, possibly seeking cold-water, potentially in an effort to to achieve metabolic homeostasis. This pattern started once refilling of Lake Roosevelt began in May 2010. Once the reservoir began to refill, Lake Roosevelt became more lentic, which allows water temperature to rise faster. During reservoir drawdown, the kokanee tended to show a preference to move downstream with the current. This could have been due to kokanee following their zooplankton prey as they were moved downstream in the current. During refill, the 2 kokanee that were still being actively tracked did not have a preference for moving upstream or downstream. One fish moved upstream, and the other moved downstream. Three fish were documented entraining over Grand Coulee Dam, with an additional 7 fish showing a similar pattern of entrainment. These 7 fish were last detected near the forebay of Grand Coulee Dam, but were not detected at the Rufus Woods receiver below Grand Coulee Dam. No primary spawning locations were found during this study. However, one kokanee did make a 292.8 km migration from Grand Coulee Dam up to Hugh Keenleyside Dam in British Columbia, Canada. This fish made the migration in 26 days at an average pace of 11.3 km per day. It was presumed that this fish was returning to its natal tributary in the Arrow Lakes but was blocked from passing Hugh Keenleyside Dam.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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