Fish Ladder

Fishways, most commonly called fish ladders but also known as fish passes and in Australia they are referred to as fish steps, are structures on or around artificial barriers (such as dams and weirs) to facilitate diadromous fishes' natural migration. Most fishways enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps (hence the term ladder) into the waters on the other side. The velocity of water falling over the steps has to be great enough to attract the fish to the ladder, but it cannot be so great that it washes fish back downstream or exhausts them to the point of inability to continue their journey upriver.