DILLINGHAM, Alaska—In the remote and undeveloped hills northeast of here, the clear waters of great sub-Arctic rivers and their tributaries carve an intricate web across the tundra. Upper Talarik Creek flows into Lake Iliamna, one of the largest lakes in North America and home to millions of sockeye salmon, and Lake Iliamna empties into the Kvichak River. The Koktuli and Stuyahok flow into the Mulchatna River, which flows into the broad Nushagak. In time, all of these waters flow into Bristol Bay, perhaps the most productive wild salmon fishery remaining in the world.