Northern Lights Fly Fishers recently produced a slide presentation on the primary natural food items that trout find to eat in Alberta's lakes along with fishing tips to imitate those items at each stage of their lifecycle. It also has embedded links to over 130 articles and videos for those looking for even more information. It was put together by some very experienced stillwater anglers with the help of an aquatic entomologist, a fisheries biologist, and an education consultant. There's some great photos in it too. It's well worth checking out.
What Trout Eat - Digital Version
https://www.nlft.org/what-trout-eat-digital/