The Middle Prong of Little River (Tremont) is open for fishing all the way up to the parking area at the end of the gravel road. At that point there is a footbridge that crosses Lynn Camp Prong. Lynn Camp goes off to your left and is closed to fishing (there are signs posted). The branch to the right is Thunderhead Prong and you can fish it (and its feeders) as far up as you care to hike. Enjoy yourselves.
Fly fishing - it's cheaper than a bass boat!