During August 2003 and July-August 2011, the Alaska Department of Fish and Game, Division of Sport Fish conducted an inventory of stream fish assemblages and associated aquatic and riparian habitats in a 53,445 square-km. study area comprising the upper Cook Inlet basin bounded by the Alaska Range to the north and west, the Chugach Mountains to the south, and the Copper River basin to the east. (In addition to the Susitna River watershed, this included Maguire Creek and the watersheds of the Matanuska and Knik rivers.) Some 357 study sites were visited in streams ranging in size from wadeable headwaters to the mainstem Susitna River. At each site, data was collected describing site location, aquatic habitat, riparian vegetation, and fish-assemblage composition. Fish were collected primarily using backpack and boat-mounted electrofishers. In total, 19 fish species, representing 12 genuses, and 7 families were found. Anadromous fish were documented at 114 study sites. As a result of this inventory, a total stream length of 830 km. of previously unlisted anadromous fish habitat was added to the State of Alaska's "Catalog of Waters Important for the Spawning, Rearing or Migration of Anadromous Fishes." The primary fish-collection gear type used was single-pass electrofishing.