Fish passage: how does it work?


The higly migratory fish life cycle

All along their life, highly migratory fish travel between the ocean and fresh water throughout the different phases of their biological life cycle. So the salmon, the sea trout, the mayfish, the lamprey and the sturgeon swim up the waterways in order to reproduce in their spawning ground. The young salmon for example, stays bewtween one and three years in a stream, then when he is as big as a sardine, he joins the sea, offshore Greenland, and stays there until he is sexually mature. One to three years later, he will comme back to the river where he was born in order to reproduce.

The principle of the fish way is simple

The point is to attract migratory fish to an artificial waterway which passes around from downstream, the insurmountable hydraulic construction. Since migratory fish typically swim against the current, a flow of about 15 m3/s, is deviated towards the inlets of the fish passage. Thanks to that natural steering, salmon, sea trouts and other fish species enter the fish way. In Gambsheim, they climb a height of 11 Meters, crossing successive pools linked to each other by vertical slots. After he has passed each little difference in height, the fish can rest in the upper pool.

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