Lots of cutthroat in the Harrison this time of year, just have to find them.
We will usually target them with a spinning rod and files, small spoons and minnow patterns. Locating them is the key, usualy keep a close eye out for any surface activity as they'll be schooling up salmon fry. If we see any ripples or a splash can usualy gurantee a few fish in that location. We concentrate on the back water areas where the water is calmer.
Casting and stripping thin streamers/minnows has proved effective in the past, light green belly with a darker back has always worked well for me, i have found very thin to work better than a thick fly, like literally only a dozen strands of dyed fly tying hair (not sure name, deer tail?) Another fly is a green flash chenille/mariboo tail with gold headed bead, added weight to this fly like a wrap of lead on the body helps to get it down a little faster. Will use a floating line and cast around the ripples stripping a foot or so 2-3 times then pause.
Another go to would be a stone fly in blk/gold bead. Always in the fraser year round and work amazing when you can locate some fish. Either fished dead drift under a strike indicator or casted with a floating line, let it sink all the way down and do small 2-3" tugs with a pasue every 10 seconds or so, don't know if this is the proper way to fish them but has worked well for me.