Banks Lake Fishery Evaluation Project (Project 200102800)

1. Banks Lake Fishery Evaluation Project(Project 200102800) Matt Polacek, Project Manager Washington Department of Fish and Wildlife

2. Objective and Purpose • To re-establish a once popular and successful kokanee fishery in Banks Lake to provide a salmonid fishery above the blocked area. • Established as an M&E program for kokanee planted by the Ford Hatchery (200102900).

3. Banks LakeStudy Area

4. Project History • This Project was funded by BPA in 2001 to evaluate game fish populations in Banks Lake. • Identifying limiting factors to kokanee became the primary objective due to their popularity in regional fisheries. • Baseline data collections began in 2002.

5. Historical Kokanee Fisheries P/G Units Operational (1974) • The BLFEP conducted M&E studies, examining: • Limiting Factors and 2. Success of differing kokanee release strategies SMB Planted 1981 Barrier Net Installed 1978 Walleye Stocked (1990's) Net Pen kokanee rearing 2002

6. Limiting Factors • Evaluate factors that limit kokanee survival • Exploitation (creel) • Zooplankton availability • Water conditions and quality • Entrainment • Predatory impacts (bioenergetics modeling)

7. Results - Limiting Factors • HIGH IMPACTS • Prey Availability - Whitefish consumption exceeded Daphnia biomass in the winter and summer months • Whitefish abundance is of concern (90% composition) • Predation - Walleye predation was the leading source of mortality based on diet analysis and bioenergetics modeling. • LOW IMPACTS • Water quality • Exploitation (< 2,000) • Entrainment (< 3,000)

8. Results – Prey Availability

9. Walleye Predation on Kokanee • Bioenergetics Modeling • Over 8 million grams of kokanee were consumed in one year • Equates to an estimate of over 950,000 fry • Age 2 (size 12” – 14”) – consume 35% • Age 3 (14” – 19”) – consume 31% • Age 4 (19” – 22”) – consume 16% • Age > 4 (up to 32”) – consume 18% • Acute predation during releases is substantial

10. Kokanee Release Strategies • Maximize hatchery kokanee survival • Differing release and rearing strategies • Spring fry • Fall fingerlings • Net pen yearlings • Each group was differentially marked using thermal otolith marking or fin clips • Null Hypothesis: The proportions of each release group is not significantly different than the proportions collected in the fall as adults.

11. Rejected the Null Hypothesis (P < 0.001) Release Strategy Results Fall fingerlings Net pen yearlings Tested Brood Years 2002 – 2005 Used chi-square analysis with Yates correction. Spring fry

12. Adaptive Management We recognize that the “status quo” is not working • Predation issue • Lake whitefish competition issue • Recruitment to the creel is not meeting expectations Therefore, We propose to build on past results to implement new strategies to increase kokanee survival

13. Banks Lake Kokanee Decision Tree Goal for kokanee in Banks Lake: 0.5/hr; 20-30/ha; 10,000 fish harvest goal Further Refine Release Success to address acute predation Address Walleye Predation Address Competition with Lake Whitefish Fall fingerlings Refine current bag limits to reduce the # of “teenage” walleye Implement mechanical removal program Use existing data, case studies, modeling, and outreach Day/shore Night/Barge Goal: Reduce Lake Whitefish population by 30% by year 5 Consumption reduced by 35% by year 5 Consumption not reduced by 35% by year 5 Monitor Population: hydroacoustics and CPUE Monitor population: creel, hydroacoustics, and CPUE Monitor Population: creel and FWIN CPUE; consumption Goal met or nearly met Goal not met Goal met or nearly met Goal not met Continue to monitor water quality and zooplankton Continue stocking using best strategy Continue Kokanee Stocking Discontinue Kokanee Stocking

14. The Future of Kokanee in Banks Lake • Continued stocking of kokanee will depend on how close goals are met • If not kokanee, then WDFW managers will implement a new strategy (i.e. increase rainbow trout production) to provide a salmonid fishery above the blocked areas.