I know there are a lot of bullheads in there, ha
Apparently there are sturgeon in there at times although I have yet to catch one, but there is carp as well and I do know that for a fact.
I would imagine there is cuttthroat in there too, I know there are a few rainbows as I have caught some smaller ones in the 8 -12 inch length. Actually on bread of all things under a bobber while I was fishing for carp. That was actually the first place I ever caught trout on bread.....
If memory serves me right there is an age restricted creek (I can't remember the name off hand) that flows into the Sumas that they used to stock with rainbows at one time, not sure if they do anymore, so I am not sure if they are from their or just resident rainbows.