I have an alternative theory to put forth, as devils advocate if you will. I am old enough to remember the fishing in Deif in the '80s, pre-spawn camp era. That was in the time when burbot were regarded as garbage fish, had no limit and were left on the ice in huge piles for the crows and coyotes. What if people did so much damage by removing a tertiary predator from the ecosystem that it affected the walleye population down the road. Young burbot are a food source for walleye. And Burbot eat young walleye, so that predator being removed meant a walleye boom perhaps. Now add the trout released over the time period of the spawn camp, and you have added another tertiary predator to the ecosystem in the walleye spawning grounds. Add the huge influx of white suckers in Coteau and you have an opportunistic fish that eats anything it can (ie; eggs). Burbot are now on the rebound in deif and they also eat eggs/young walleye. I'm not trying to belittle anyones work or efforts, what I'm trying to show is that Limnology is a very complicated science. To pin the decline of something on one thing is usually incorrect. It is usually a series of things, often not related, that lead to a result you notice. Which is why I gave the above suggestion.