I used to live in Squamish in the 1970s and even in the "good old days" the Mamquam was never good for trout. I waded across it every day on my way to work. I caught steelhead in the spring and the occasional char, but no cutthroat. The only cutthroat I caught were down in the estuary. I caught Bull trout and resident rainbows far up the Squamish above the Ashlu, but steelhead were the main target. I've fished the Cheakamus from one end to the other and the best fishing for it was up near Daisy Lake. As someone already mentioned, the trout were small. I used to hike down below Brandywine falls and fish that stream all the way to the lake. It DID have good trout fishing, but I'm not sure how it is today. Other than the Fraser River itself, there are not a lot of good trout streams close to the Lower Mainland, and that is why so many people fish the Skagit.