IMIS

The researchers investigated the efficiency of smolt downstream migration in the lake that feeds the Anundsjo hydropower plant (Bredbyn, Sweden). Specifically the migration speeds and routes were evaluated and the predation risk was estimated. The lake contains a debris catcher and a fish guidance screen that should guide fish to a fish ladder that by-passes the hydropower plant. Sixty hatchery reared salmon smolts were surgically implanted with VEMCO V5 acoustic transmitters to study their downstream migration behavior. Forty of them were released in the river upstream of the lake and the hydropower plant and 20 smolts were released downstream of the hydropower plant in the residual flow of the lake. Only half of the released fishes reached the lake. Thirty five per cent of them entered the hydropower plant and were not observed downstream. The others were predated in the lake. None of the fishes found the entrance to the fish ladder. The results were used to advise local managers. more