Upper Shaver's Fork River, Potomac Highlands, W.Va.
The rainbow trout in the Upper Shaver's Fork, which courses through the state's highest peaks in 900,000-acre Monongahela National Forest, have a bit of an obesity problem. These unusually hefty swimmers routinely grow to 20 inches, thanks to the river's fertile, insect-grabbing gravel bottom. No chance of anglers developing the same condition, though: These big boys are catch-and-release. Fishing permit, $2; 800-225-5982; callwva.com