I just fished Kachess for 3 days this last week. The Northern Pikeminnows were dominated the game all around the campground area of the lake. I pulled in probably a dozen of these guys each day I fished, ranging between 8" to about 14". The shallows were chuck full of planted trout/kokanee fry that these fish were no doubt feasting on.
Mostly trolled with Rooster Tails and Dick Night spoons. Also able to catch a few from shore right at the boat launch using balls of fire salmon eggs.
WDFW better start paying attention to these guys, otherwise all their hard work to plant this lake is going to be lost. Just my 2 cents...