Project Summary for the Monitoring and Evaluation of Limnetic Fish Surveys and Examination of Some Limiting Factors for Kokanee and Rainbow Trout in Lake Roosevelt, Washington, 1998-2010
Author: Danny Didricksen
Publisher:
Published: 2011
Total Pages: 0
ISBN-13:
DOWNLOAD EBOOK"A collaborative research effort took place between the Spokane Tribe of Indians, the Colville Confederated Tribes, and the Washington State Department of Fish and Wildlife, on Lake Roosevelt, WA. Data was collected between 1998 and 2008 in order to better understand the limnetic habitat and spatial distribution of fish within it. This report summarizes the work done by the Washington State department of Fish and Wildlife during that time period. Special emphasis and consideration were given to abiotic habitat conditions, spatial distributions, and potential limiting factors, to kokanee and rainbow trout. These are the game species stocked in the lake and what the lake is managed for in terms of recreation and subsistence. The only consistent potential environmental strain these fish must withstand is thermal habitat compression of the upper strata (>15C) during the late summer in the lower section of the lake, especially for kokanee, forcing them to vertically migrate into suboptimal conditions to obtain their primary prey item, Daphnia. Despite this potential thermal stress, overall fish health remains strong as indicated by high relative weights of 102.6 and 97.3 respectively for wild origin and hatchery origin kokanee. In similar fashion, wild rainbow trout had a relative weight of 98.1 and hatchery origin rainbow trout had a value of 99.0. This viewed in combination with relatively large spawner lengths for kokanee of 310 +-18 mm (SE=4.9) and 423+-43 mm (SE=11.6) for age-2 and age-3 fish respectively compared to other kokanee bearing systems in the western United States. Hydroacoustic surveys indicated that fish density decreased from the upper section of the reservoir to the lower section but conversely kokanee distribution, while patchy, was found to be opposite that pattern according to gill net surveys. The ten-year study period provided a dynamic view of how target species utilize the limnetic habitat and shows that while some environmental pressures exist, Lake Roosevelt provides quality limnetic habitat for kokanee and rainbow trout."--Abstract (page i).
