Underwater invaders: Many invasive species pose threats to lake

On a dock that leads from the pine-bordered shoreline of Flathead Lake, I lean over and look into the clear green water as hundreds of native Northern pike minnow swim carefree through the gaps of timber structure of the dock. In the warming water of spring the fish are spawning. I have watched them since my childhood carrying out the same cycle year to year by playfully swirling around each other.