Lake Roosevelt Fisheries Evaluation Program : Lake Whatcom Kokanee Salmon (Oncorhynchus nerka kennerlyi) : Investigations in Lake Roosevelt Annual Report 1999-2000.

Abstract

Lake Whatcom stock kokanee have been planted in Lake Roosevelt since 1988 with the primary goal of establishing a self-sustaining fishery. Returns of hatchery kokanee to egg collection facilities and recruitment to the creel have been minimal. Therefore, four experiments were conducted to determine the most appropriate release strategy that would increase kokanee returns. The first experiment compared morpholine and non-morpholine imprinted kokanee return rates, the second experiment compared early and middle run Whatcom kokanee, the third experiment compared early and late release dates, and the fourth experiment compared three net pen release strategies: Sherman Creek hatchery vs. Sherman Creek net pens, Colville River net pens vs. Sherman Creek net pens, and upper vs. lower reservoir net pen releases. Each experiment was tested in three ways: 1) returns to Sherman Creek, 2) returns to other tributaries throughout the reservoir, and 3) returns to the creel.Chi-square analysis of hatchery and tributary returns indicated no significant difference between morpholine imprinted and non-imprinted fish, early run fish outperformed middle run fish, early release date outperformed late release fish, and the hatchery outperformed all net pen releases. Hatchery kokanee harvest was estimated at 3,323 fish, which was 33% of the total harvest. Return rates (1998 = 0.52%) of Whatcom kokanee were low indicating an overall low performance that could be caused by high entrainment, predation, and precocity. A kokanee stock native to the upper Columbia, as opposed to the coastal Whatcom stock, may perform better in Lake Roosevelt.3

Walleye Predation on Hatchery Releases of Kokanees and Rainbow Trout in Lake Roosevelt, Washington

“…Release of larger fish might increase rainbow trout survival, but rearing kokanees to larger sizes would likely increase the rate of precocity, thereby reducing the number of age-3 fish recruiting to the fishery and returning to egg collection sites (Patterson 1998). Kokanees have been released from other areas in the reservoir, including the Spokane River below Little Falls Dam, Seven Bays near the confluence with the Spokane River, and Lincoln (near Hawk Creek) without substantially better returns than the northern release sites (Tilson and Scholz 1998;McLellan et al 2001). A change in the walleye regulation has already been submitted to the Washington Department of Fish and Wildlife that would allow harvest of walleyes between 406 and 508 mm (the previously protected slot limit).…”

Lake Roosevelt Fisheries Evaluation Program; Limnological and Fisheries Monitoring, Annual Report 2000.

“…1) Evaluation of hatchery kokanee returns to egg collection facilities (Eastern Washington University) (McLellan et al 2001).…”

Lake Roosevelt Fisheries Evaluation Program : Meadow Creek vs. Lake Whatcom Stock Kokanee Salmon Investigations in Lake Roosevelt Annual Report 2000-2001.

“…The primary purpose of the stocking was to develop a self-sustaining sport fishery and restore a migratory salmonid species to the Lake Roosevelt ecosystem. In 1990, kokanee were coded wire tagged to evaluate planting strategies (Scholz et al 1992, Tilson et al 1994, 1997, Tilson and Scholz 1998, McLellan et al 2001).…”

“…In each year, a jack run composed primarily of precocious males was approximately 0.2-0.5% of the total fish stocked (McLellan et al 2001). However, age 3 male and female spawners still failed to return the following year.…”

“…For all Whatcom cohorts stocked, the number of age 3 spawners has been far less than the number of age 2 jacks that returned. For example, the 1996 cohort 2,441 age 2 kokanee were collected in 1998 and 28 age 3 kokanee in 1999in . (McLellan et al 2001.…”