I've only been exploring the area for fishing spots for a few weeks, but the Oirase River, after it outlets from Lake Towada, had some nice spots to catch Rainbow Trout and Steelhead. I follow the river, and try out a few spots here or there. Fishing is prohibited, however, between the Oirase Bridge, and the mouth. As long as you stay away from the coast, you'll be fine. Good luck!