Development and Performance of an Alaska Steeppass Fishway for Sockeye Salmon (Oncorhynchus nerka)

Abstract

A major introduced run of sockeye salmon (Oncorhynchus nerka) at Frazer Lake, Kodiak Island, Alaska, is perpetuated by an Alaska steeppass fishway at a 10-m-high falls on the outlet river. Experimental modifications of the fishway, which was inadequate by 1970 as the salmon run increased, improved salmon entry and passage. Sockeye passage over 4 yr was nearly equivalent in a steeppass of 60 m continuous length (22% slope) and an adjoining steeppass with three resting pools, but significant year-to-year differences in passage occurred between steeppasses. Resting tanks were beneficial for holding slower or descending salmon without blocking passage of other salmon. An average entry of 142 sockeye in 15 min was achieved by guiding all salmon along a weir to an entrance tank with a vertical slot orifice. Chutes installed in the entry end of the steeppasses created a high-velocity stream for attraction and decreased salmon dropout from the entrance tank. Salmon passage in the original steeppasses with three resting pools was greater than in new (1979) steeppasses with a single resting pool. In 1985, sockeye passage of 2925/h and 46 806/d exceeded fishway capacity requirements.