The answer here is genetic selection. Pike hatch 2-3 weeks earlier than musky and prey on musky fingerling when they first hatch. Musky that don't grow quickly end up as pike buffet. Over the coarse of evolution only the fastest growing largest musky where able to survive in waters which held pike. The work of Bernard Lebeau is great if your into the science. He postulates that there are two different and distinct musky species. Lacustrine(which evolved without interaction with pike) and Riverine(with pike) As far as the Kawarthas go we are talking evolution so musky co-existing with pike there will take 100's of generations before any gentic drift will happen so it might never happen.