Fish ladders (also called fish ways and fish passes) are used to help fish get upstream to spawn. When dams and other obstructions are created in a stream or river, it is sometimes necessary to help the fish so that they can continue to do their part in the river ecosystem.
Types of Fish Ladders
There are 4 basic types of fish ladders[1]. All of these examples can be found around the United States, but some are used more often on larger waterways than others.
- Pool-Weir
Used most often at man-made passageways and are the oldest type of fish ladder
- Vertical Step
Uses a ladder-type step formation and is more complicated than the Pool-Weir type. The benefit is that it allows the water to flow at its own rate.
- Denil
- Steep Pass
Why do we need fish ladders?
It was found that entire fish species were either close to extinction or totally extinct because they had no ability to reproduce. It is known that some species of fish must migrate upstream to find a suitable place to spawn, and these man-made obstacles made that virtually impossible.