fish pass
dam structure
Quick Summary
Fish passes are structures designed to help fish navigate around or over dams. These structures are crucial for maintaining fish populations, particularly migratory species like salmon, which need to travel upstream to spawn and downstream to reach the ocean.1
Two common types of fish passes are:
- Fish ladders: These consist of a series of pools arranged like steps, allowing fish to swim upstream over a dam. Water is continuously discharged through these pools during migratory seasons, with each pool separated by low weirs or short pipes.21
- Fish lifts (or locks): These devices function similarly to an elevator or conveyor belt, transporting fish upstream over an obstruction. Developed as an alternative to ladders, they operate on an intermittent principle, raising fish from a lower chamber to the top of the dam.31
While these technologies have seen success in certain areas, the increasing number of dams has led to significant declines in migrating fish populations on some rivers.1
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