This unit consists of all Gulf of Alaska and Prince William Sound drainages from the center line of Icy Bay (excluding the Guyot Hills) to Cape Fairfield, including Kayak, Hinchinbrook, Montague, and adjacent islands, and Middleton Island; but excluding the Copper River drainage upstream from Miles Glacier, and excluding the Nellie Juan and Kings river drainages.
Unit 6A consists of Gulf of Alaska drainages east of Palm Point near Katalla including Kanak, Wingham, and Kayak islands.
Unit 6B consists of Gulf of Alaska and Copper River Basin drainages west of Palm Point near Katalla, east of the west bank of the Copper River, and east of a line from Flag Point to Cottonwood Point.
Unit 6C consists of drainages west of the west bank of the Copper River, and west of a line from Flag Point to Cottonwood Point, and drainages east of the east bank of Rude River and drainages into the eastern shore of Nelson Bay and Orca Inlet.
Unit 6D consists of the remainder of Unit 6.