Tough lake to find fish in. There really aren't many in there. Do you have a boat?? The Channel that comes out of the old dam used to be a decent spot to fish, and off of the old wooden bridge near the mouth of the channel. But they have closed off access to the whole channel, and put fences on the bridge. Since they started work on the dam a few years back, they've been fluctuating the water levels more often than usual, and it seems to have distruped the balance of things in that lake. It's a very tough go right now. The stave lake boat launch (right up the road) may be a better bet. Last weekend the docks weren't in yet, and the water was down a bit, but you could still fish off of the rocks there. Probably a better bet than Hayward. Stave is a much more productive lake.
As far as target species, there is a mixed bag in both, but primarily you are fishing for pikeminnow and Cutties if you're shore fishing, with the possibility of targetting bulls/dollies if you have a boat. If you HAVE to fish at Hayward, and don't have a boat, I would try parking near the dam at the South end, and walking up the trail to the rock bluffs etc. There are more and better options at that end of the lake. If you're stuck in the park at the North end, try the beaver pond for trout and pikrminnows/suckers. Or possibly down around the dog beach if it's not too busy. There really aren't many shore fishing options left at that end of the lake anymore. Good luck and let us know how you make out.