Fish ladder
A fish ladder, also known as a fishway, fish pass, fish steps or fish cannon, is a waterway structure on or around artificial and natural barriers (such as dams, locks and waterfalls) that provides aquatic animals (particularly fish) a "detour" to facilitate natural movements and migrations of diadromous and potamodromous species. Fishways enable fish to pass around the water level difference around barriers by swimming and/or leaping up a series of relatively low stepped spillway (hence the term ladder), which is built in the form of a small, serpentine, low-discharge canal to the side of the barrier.