An interesting question with no definite answer. I imagine you will gat a variety of opinions on your question.

I believe I would start with nymphs, using any of the more popular patterns, say in size 10 or 12. I would let it sink about 3/4 of the way to the bottom and retrieve with slow twitches. I would not be afraid to keep changing flies until I found something that produces.

In addition I would pay attention to what other fly fisherman are doing and if they are successful you might want to copy them.

Good Luck
Tim