Laboratory Evaluation of a Denil-Type Steeppass Fishway with Various Entrance and Exit Conditions for Passage of Adult Salmonids and American Shad

This research was designed to determine the feasibility of using a Denil-type fishway as part of a system to trap marked adult salmon and trout ascending a pool-and-overfall fishway at Little Goose Dam on the Snake River. Several entrance and exit situations were tested along with two methods (hollow weir and a pool) of supplying water to the Denil. Water supplied directly to the Denil through a hollow weir provided the best passage conditions for chinook salmon (Oncorhynchus tshawytscha), sockeye salmon (0. nerka), steelhead trout (Salmo gairdneri), and American shad (A.lo~a sapidissima). Salmonids and shad readily entered and ascended a Deml flshway when the downstream end was submerged to a depth of 2.5 feet (0.7 m). Chinook salmon, coho salmon (0. kisutch), and steelhead trout readily passed through a Denil steeppass fishway that was 50 feet long (15.2 m) and pOSItioned at a slope of 28.7 percent. fish to an auxiliary steeppass which requires ascent to a height above the primary fishway. On reaching the apex of the steeppass, the fish descend a chute which discharges them past the detector head at the required velocity. Untagged fish are returned directly to the primary fish way , whereas tagged fish are automatically deflected into a holding trap. Another transportation experiment is presently in progress at Little Goose Dam on the Snake River, and a comparable automatic detection and separation system was needed for pickup of wire-tagged adult salmon. Although the detection and collection system used at lee Harbor incorporated a steeply sloped pool-and-overfall fish way . space limitations in the fish way at Little Goose Dam precluded use of a pooltype fishway. However, previous experiments at the Fisheries-Engineering Research Laboratory on slopes of Denil steeppasses indicated that a Denil fishway would be suitable for adaptation at Little Goose Dam. Before installing the Denil in the fishway at Little Goose Dam, we needed to know its effect on fish passage. Therefore, in 1971, we conducted experiments with the Denil fishway to determine the best entrance and exit conditions and to assess the affect on fish passage through the Denil when placed in a prototype I-on-IO-slope, pool-and-overfall fish way . This information is described herein and was lIsed in the final design of the automatic detection and separation system installed at Little Goose Dam. Emil Slatick is a member of the staff of the Northwest Fisheries Center, National Marine Fisheries Service, NOAA, 2725 Montlake Boulevard East, Seattle, WA 98112. EQUIPMENT AND PROCEDURES This study was conducted at the Fisheries-Engineering Research Laboratory located at Bonneville Dam on the Columbia River(Collins and Elling, 1960). The laboratory is an enclosed rectangular flume 180 feet (54.9 m) long, 24 feet (7.3 m) wide, and 24 feet (7.3 m) deep, located adjacent to the Washington shore fish ladder on the in an effort to find solutions to the complex fish passage problems caused by dams on the Columbia and Snake Rivers. Since 1968 considerable effort has been centered on transportation experiments designed to determine whether collecting juvenile salmonid migrants at upstream dams and transporting them downstream around hazardous areas, such as turbines at dams, might be a feasible method of reducing losses during downstream migration. Evaluation of these studies is based on returning adults. To properly evaluate these experiments, an automatic system was needed to detect and separate wire-tagged (Jefferts et aI., 1963) adult salmon during ascent of a fishway. Durkin et al. (1969) described and tested a prototype system at Minter Creek Hatchery, and Ebel et al. (1973) used this system successfully in the fish ladder at Ice Harbor Dam to evaluate a transportation experiment. A basic requirement of the detection system is that the fish must pass the detector head at a velocity of about 1.0 mJs. This can be achieved in a conventional fishway by directing the