04-08-2003, 12:31 AM
[font "arial, helvetica, sans-serif"][#00e010]What is a Fish Ladder[/#00e010][/font]
[font "arial, helvetica, sans-serif"][black]A fish ladder (or fish way, fish pass) is a structure designed to allow fish the opportunity to migrate upstream and continue their function as part of the river ecosystem. Fish ladders may be recommended when blocking structures are as low as 1 to 2 feet in height. Critical components to determine when a ladder is necessary are the water depth below the blockage, the water velocity, and the type of species that need to pass.
Many design factors are looked at by engineers when designing and placing a structure. Every blockage in a river represents a unique situation and challenge, and each fish ladder is therefore carefully designed and placed. No one fish ladder design will accommodate most species of fish. Each species has different physical characteristics that need to be taken into consideration when designing passage facilities. Flows, energy dissipation, resting areas, drop between pools, attraction velocities, entrance eddies, and space in pools are just some of the factors that need to be considered when designing a ladder.
Types of Fish Ladders
There are four basic designs for fish ladders that are used throughout the world. All four can be found in Michigan, but two types are primarily used especially on large water such as the St. Joseph or Grand Rivers.
Pool-Weir
![[Image: poolweir_57674_7.jpg]](http://www.michigan.gov/images/poolweir_57674_7.jpg)
The pool and weir fishway is used at man-made structures and are the oldest of the fishway designs.
Vertical Slot
Vertical slot ladders are quite common. They repeat a constant flow pattern at all operating depths. Its design is less simple than a pool and weir design, but its advantage is that it is self regulating in terms of flow.
Denil
Site not constructed yet.
Steep Pass
Site not constructed yet.
Why Do We Need Fish Ladders?
It was recognized long ago that obstructions in rivers such as dams fragment aquatic ecosystems and affect fish populations. France developed fishway laws during the 1660’s requiring passage be built into new dam structures. Fragmentation of rivers can and has resulted in the decline and in some cases a complete loss of fish species. Species such as steelhead, chinook salmon, or suckers are particular susceptible to declines from impassable river obstructions. The life history of species such as these requires that they migrate upstream to find suitable spawning locations. Thus, effective passage can be critical to the protection and recovery of many fish stocks. [/black][/font]
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[font "arial, helvetica, sans-serif"][black]A fish ladder (or fish way, fish pass) is a structure designed to allow fish the opportunity to migrate upstream and continue their function as part of the river ecosystem. Fish ladders may be recommended when blocking structures are as low as 1 to 2 feet in height. Critical components to determine when a ladder is necessary are the water depth below the blockage, the water velocity, and the type of species that need to pass.
Many design factors are looked at by engineers when designing and placing a structure. Every blockage in a river represents a unique situation and challenge, and each fish ladder is therefore carefully designed and placed. No one fish ladder design will accommodate most species of fish. Each species has different physical characteristics that need to be taken into consideration when designing passage facilities. Flows, energy dissipation, resting areas, drop between pools, attraction velocities, entrance eddies, and space in pools are just some of the factors that need to be considered when designing a ladder.
Types of Fish Ladders
There are four basic designs for fish ladders that are used throughout the world. All four can be found in Michigan, but two types are primarily used especially on large water such as the St. Joseph or Grand Rivers.
Pool-Weir
The pool and weir fishway is used at man-made structures and are the oldest of the fishway designs. Vertical Slot
Vertical slot ladders are quite common. They repeat a constant flow pattern at all operating depths. Its design is less simple than a pool and weir design, but its advantage is that it is self regulating in terms of flow.
Denil
Site not constructed yet.
Steep Pass
Site not constructed yet.
Why Do We Need Fish Ladders?
It was recognized long ago that obstructions in rivers such as dams fragment aquatic ecosystems and affect fish populations. France developed fishway laws during the 1660’s requiring passage be built into new dam structures. Fragmentation of rivers can and has resulted in the decline and in some cases a complete loss of fish species. Species such as steelhead, chinook salmon, or suckers are particular susceptible to declines from impassable river obstructions. The life history of species such as these requires that they migrate upstream to find suitable spawning locations. Thus, effective passage can be critical to the protection and recovery of many fish stocks. [/black][/font]
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