It has perch, walleye, and trout. If there is another species in there, I don't know of it. It would be a great smallmouth lake, but I don't think there are any populations in there. It also may have bullhead catfish. There are some large walleye in there. The perch all seem to be short and very fat!
Are you bank fishing? It is a difficult spot to bank fish because of the sheer cliffs. Where you can walk to the water, you can still catch fish. I have caught walleye off the dam in the morning. If you boat it, fish around the spill tower. Fish like to hang around it. It's going to be cold and tough fishing for another month at least. June will probably be best. Also, you may see some ... interesting people. Be careful there as the bank with its cliffs is very treacherous. However, there are some nice perches there for fishing off the cliffs. Lots of shale there if you need some rock to decorate with.
Oakley has great scenery but if you want to put fish in the cooler, go to Milner. Lots of bass, some channel cats, and right now, if you would like your limit of whitefish, they are biting. They bite light and wind can be difficult. Wind can be a problem at Oakley as well. Let me know how it goes. I miss that old lake.