I have been pondering this a while,
Me and my brother were camping a couple springs ago, about the time of the trout spawn, and we found 100's of clams in this little lagoon that was basically a lake with a creek booked by a beaver dam with a 2 foot wide creek still going through it. anyway in about 3 feet of water were all these clams or muscles, what ever they are, we brought come back to came and cooked them, but then I remembered reading on some survival good about them being inedible in april or something, and cause it was a 3 mile canoe paddle and another 5 mile hike back, we didn't wan a be dying on the way out or something cause it was back before we had cell phones.
so this was about the middle of the trout spawn. maybe closer to the end....don't remember what month, but I remember the clams were about 4 or 5 inches across, the bigger ones, and most were 3 or 4 inches, so are they edible?