1. Idaho Department of Fish and Game Clearwater Region Lewiston Idaho EVALUATE AND CONTROL BROOK TROUT POPULATIONS IN NORTHCENTRAL IDAHO WATERSHEDS : ADDRESSING IMPACTS OF COMPETITION AND HYBRIDIZATION WITH BULL TROUT

2. ISSUES Brook trout may effectively displace or replace native bull trout through competition, predation, and hybridization. Downstream brook trout invasions may be the single most important negative impact to native bull trout in protected watersheds. Threats associated with hybridization may be more prevalent and important than previously documented.

3. PROTECTION OF NATIVE BULL TROUT Suppression of brook trout may be vital in protecting threatened bull trout in relatively protected watersheds

4. Are introduced, mountain lake populations of brook trout negatively affecting downstream populations of bull trout in watersheds of northcentral Idaho?

5. OBJECTIVES Suppression of brook trout in mountain lakes and headwater tributaries. Document the distribution and abundance of bull and brook trout in Clearwater River drainage. Document hybridization of bull trout populations with brook trout.

6. Suppression Techniques Sterile Tiger Muskies Electrofishing

7. APPROACH Implementation and monitoring of suppression techniques. Snorkel survey methodologies to document distribution and abundance. Collection of genetic samples (using mitochondrial and nuclear DNA) to document hybridization.

8. WHAT WE KNOW TO DATE ~ 50 headwater mountain lakes have naturally reproducing populations of brook trout. ~ 40% of these lakes, are located within the Selway-Bitterroot Wilderness. Downstream invasions and colonization of brook trout is occurring. The distribution and abundance of both species is limited and uncertain.

9. PRODUCT Prioritization and development of brook trout suppression efforts. Documentation of introduced and native species distribution and interactions. Documentation and assessment of hybridization threats. Protection of native salmonids.