Efficiency of a fish lift for returning Atlantic salmon at a large-scale hydroelectric complex in France

This study describes the behaviour of radio-tagged returning Atlantic salmon, Salmo salar L., at the Golfech-Malause hydroelectric complex on the River Garonne, France. The particularity of this complex is that it is fitted with a fish lift, a type of fishway rarely tested for salmon. Only forty seven percent of salmon succeeded in passing. Frequenting of both the tailrace and the foot of the plant, where the lift was located, decreased rapidly during the blockage. Successful salmon spent proportionally more time near the entrance of the lift. The high mean number of visits to the lift entrance before upstream passage (51) suggested the lift was not sufficiently attractive. Evidence is also given of the difficulties specific to fish lifts that involve trapping fish: the V-shaped entrance of the fish lift holding pool could inhibit salmon without even guaranteeing a non-return effect.