Saint Lawrence River
Adult eels migrate downstream to return to the sea for reproduction. Dams that impede juvenile eels during their upstream migration also impede adult eels going the other way. Going downstream however, eels find the only way through is by using the turbines. At Beauharnois on the Saint Lawrence River, the mortality rate for eels going through the turbines is approximately 16 to 24 %.
For a number of years, scientists have been looking for ways to keep adult eels away from hydroelectric power stations. In 2004, Hydro-Québec and MILIEU tested the avoidance of light by migrating adult eels. This species prefers to move by night and is known to have light avoidance instincts.
Three light sources were tested for this study : a submerged laser, a reflecting tunnel lighted with incandescent bulb and large incandescent spotlights. Eel were implanted with acoustic tags which permitted precise tracking of their location.