Plan B for Lake Cascade

The perch fishery in Lake Cascade might just be restored yet. Fish and Game has unveiled a plan it hopes will bring the perch back to the big reservoir that was once Idaho's most popular fishery. After the perch population crashed in the early 1990s, fisheries biologists went to work trying to determine why. A number of factors were identified, including the fact that northern pikeminnows were gobbling up young perch, preventing recovery. A recent proposal to drain the lake and treat the remaining water to eliminate pikeminnows was ultimately rejected because of possible shortages of water for salmon flow augmentation releases out of the Payette River drainage. Despite this setback, Fish and Game remains committed to restoring the yellow perch fishery in Lake Cascade, and plan B has been formulated. The restoration process faces two major hurdles: first, adult perch numbers in the lake are minimal; their offspring rarely survive beyond two years of age, a situation that has occurred regularly since the early 1990s. A second problem relates to perch predation by those pesky northern pikeminnows. The pikeminnow population was so strong in Lake Cascade in the 1990s that they effectively consumed any and all young perch produced each year. And since additional perch are not plying the waters of Lake Cascade, pikeminnows have sought out alternative food stuffs, cannibalized their own offspring. This situation has been occurring for about the last five years, leaving only adult pikeminnows in the lake. Further, the limited food supply has led to a decline in pikeminnow numbers. This situation presents a management opportunity that Fish and Game hopes to exploit. Plan "B" Plan B for Lake Cascade has been designed to address the two problems outlined above. Thousands of adult perch need to be stocked into the lake to dramatically increase the number of young perch. And the northern pikeminnow population needs to be further reduced (complete elimination is nigh on impossible). The stocking effort will require a minimum of 50,000 adult female perch (each loaded with her own complement of eggs). The idea is to have these fish spawn, producing more young yellow perch than can be consumed by the current pikeminnow population. Getting your hands on that many perch is no easy task, particularly here in Idaho where the last few drought years have all but eliminated the option of pulling perch from one reservoir and moving them to Cascade. Instead, Fish and Game staff have hammered out agreements with sister wildlife agencies in Oregon, Montana and Nevada to make the stocking effort a reality. Each agreement will allow for large-scale perch trapping operations to be conducted in reservoirs where perch are abundant. Phillips Reservoir near Baker City, Oregon, Wildhorse Reservoir near Elko, Nevada and Lake Mary Ronan near Flathead Lake, Montana have been targeted for perch trapping, not only because they hold excess perch, but also because all three reservoirs are at elevations similar to Cascade. For maximum effectiveness, perch need to be trapped right after ice-out, as they will spawn once the water begins to warm. Even now, Fish and Game crews are busy preparing for the trapping operations that will likely take three weeks at each reservoir. The plan is to capture perch using large Lake Merwin traps, placing the captured fish in floating net pens. Once enough perch have been caught and placed in the pen, they'll be loaded on a truck and hauled to Cascade for release. The plan calls for trapping and transporting efforts to take place at these three reservoirs for the next several years. While that operation is in full swing, the second half of the problem - an overabundance of pikeminnows - will also be addressed. Pikeminnow numbers will be reduced using two methods: trapping pikeminnows in Lake Cascade prior to spawning and applying a fish toxicant to the North Fork of the Payette River (and possibly the Gold Fork River) to intercept and kill spawning runs of pikeminnow. With approximately 40 percent of the spawning pikeminnow population moving up the Payette River, this method should help make quite a dent in the pikeminnow population. Both methods will also reduce the number of largescale suckers, a fish that does not consume perch, but does compete with perch for food. Like the perch trapping efforts, pikeminnow reduction will likely continue for the next few years. While these methods won't completely eliminate pikeminnows, computer modeling indicates that yellow perch survival will increase at the same ratio that pikeminnow numbers are reduced. For example, if pikeminnow numbers are reduced by 10 percent, yellow perch survival should increase by about the same amount. Between bolstering the perch population and reducing the pikeminnow population (both to be done over a several year period), the hope is that perch will eventually "take root" in Lake Cascade, leading to the exciting fishery that once thrived there. Fish and Game staff will continue to monitor the efforts, documenting results and making adjustments as needed. Remember that this effort is no quick fix. If everything goes as planned, the results everyone is hoping for - that is, large numbers of 10-inch or better perch - will not be obvious for about four years. A presentation regarding the Lake Cascade perch restoration plan will be made to the Ada County Fish and Game League at the Fish and Game Headquarters in Boise on March 31 at 7pm. Department biologists will also provide additional information at a public meeting in Cascade, Idaho in early April, date and time yet to be determined. For further information contact Dale Allen in the McCall Fish and Game Office at 634-8137.