The North Fork Clearwater River is a stronghold for cutthroat trout and bull trout due to its pristine habitat and cold, clean water. The high abundances of these beautiful, native fishes attract anglers from across the nation. However, there is a threat that many are not aware of that could jeopardize this amazing fishery in the future.
Brook trout were introduced many years ago into some of the high mountain lakes in this area, and history has shown that when conditions are right these fish can displace cutthroat trout and bull trout through competition, predation, and hybridization. Warming water temperatures in this watershed may provide the right conditions that will allow brook trout to spread from these high mountain lakes and have large-area effects on the native fishes.
Idaho Fish and Game has been aware of this threat and began efforts to remove brook trout from high mountain lakes in the upper North Fork Clearwater River watershed almost 20 years ago. These initial efforts involved stocking tiger musky into four different lakes (in the Five Lakes Butte area) in hopes that they would eradicate the brook trout through predation. 
These efforts proved partially effective in that the tiger musky significantly reduced brook trout abundance in all of the lakes, but unfortunately, they were only successful in eradicating brook trout from one of the lakes. With this understanding, Fish and Game has partnered with the U.S. Fish and Wildlife Service, Idaho Department of Agriculture, Trout Unlimited, U.S. Forest Service, and DEQ to return to the Five Lakes Butte area and finish the job it started. 
This summer, this partnership will be joining forces to rotenone Heather, Copper, Tin, and Platinum Lakes and their outlet tributaries. Evidence suggests that if brook trout are removed from these lakes that the brook trout populations remaining in the tributaries downstream will disappear without a stable source to support them.
What is rotenone?
Rotenone has been used for centuries by native tribes of Central and South America to catch fish for food. Since the 1930s, it has also been used by fishery managers to control and remove unwanted fish. 
Rotenone is a plant-derived substance that blocks a fish's ability to uptake oxygen through their gills. Rotenone works in very low concentrations (as low as 50 parts per billion), and when properly applied to ponds, lakes, reservoirs, and streams, rotenone is an extremely effective tool for fish control. For more information on the use of rotenone, follow this link: Rotenone is the "reset button" for fisheries, but what is it, and how do fisheries managers use it?
What to expect if you are visiting the area
Rotenone treatments are scheduled to occur for three consecutive weeks starting on August 11, 2025. Treatments will occur in Heather, Copper, Tin, and Platinum Lakes and the outlet streams immediately downstream of each lake. The Five Lakes Butte area will not be closed to the public; however, visitors will be asked to stay out of the treatment waters during this time. 
There will be additional traffic and Idaho Fish and Game presence in the area from July to September, and signs will be posted informing people of the project. Logistical preparations for rotenone treatments will begin in early July. Fisheries crews will collect fish in the treatment streams below the lakes and move the native species (bull trout and cutthroat trout) to adjacent streams that will not be treated with rotenone. 
Field crews will also be maintaning existing trails in the area to improve access to the treatment areas. A helicopter will be used to swing-load materials into high-elevation lakes before treatment. Campsites off Pot Mountain Road may be limited, but crews will not use Cedars Campground. The road into Five Lake Butte is narrow and rugged, so be aware of the additional traffic if you plan to visit the area. Feel free to ask the onsite crews about the project if you happen to be driving by.
What is the long-term plan?
Rotenone treatments will focus on the lakes and outlets for 2025. The lakes will remain fishless for the year immediately following the treatment so crews can evaluate the project's success and determine if any of the lakes need to be revisited for additional treatments. 
Heather, Copper, and Platinum Lakes will eventually be stocked with sterile trout to sustain fishing opportunities without risking native fishes downstream. Tin Lake will remain fishless to promote amphibian abundance in the basin.
For all questions and comments regarding the project, please contact: 
Joe.Thiessen@idfg.idaho.gov
Clearwater Regional Fisheries Biologist
Phone: 208-799-5010