Passage of north temperate fish through the Cowan Dam Denil fishway

Fish passage through a standard Denil fishway under low tailwater conditions was studied at Cowan Dam in west-central Saskatchewan in 1990. In 1991 and 1992, fish passage through an experimental two-level Denil fishway was studied at the same location under similar flow conditions. Six species of fish utilized the Cowan Dam Denil fishway in 1990; northern pike, walleye, white suckers, longnose suckers, cisco and lake whitefish. Tag returns suggest that most fish that congregate below Cowan Dam in the spring originate in Lac Ile-a-la-Crosse 150 to 200 km downstream.; Northern pike waited until spawning had been completed before ascending the fishway. Only 12.1% of pike congregated below the dam are estimated to have ascended the fishway. During both 1990 and 1991, the number of pike ascending the fishway appeared to decline as water velocities in the standard and the two-level Denil fishways increased. Mean pike length also declined over the period of fish movement, and as water velocities in the standard Denil declined. Walleye did not appear to have any difficulty ascending the standard Denil fishway in 1990, however they did appear to have difficulty ascending the two-level Denil in 1991. Only 29% of white suckers that ascended the fishway did so prior to spawning. According to recaptures of tagged fish, 58.8% of white suckers present in the tailwater pool ascended the standard Denil fishway in 1990. White suckers also appeared to be able to ascend the two-level Denil without difficulty. Ninety-eight percent of longnose suckers ascended the fishway prior to spawning in 1990. Longnose suckers appeared to ascend both the standard and two-level Denil fishways without obvious delay or difficulty. Only small numbers of cisco and lake whitefish utilized the standard Denil fishway in 1990.