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Encyclopedia > Fish ladder
Pool-and-weir fish ladder at Bonneville Dam on the Columbia River
Pool-and-weir fish ladder at Bonneville Dam on the Columbia River

Fishways, most commonly referred to as fish ladders but also known as fish passes, are structures placed on or around man-made barriers (such as dams and weirs) to assist the natural migration of diadromous fishes. Most fishways enable fish to pass around the barrier 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 as to wash fish back downstream or to exhaust them to the point where they cannot continue their journey upriver. One of several fish ladders located at Bonneville Dam on the Columbia River, here looking down the approximately 60 1-foot steps of the ladder. Photographed by Eric Guinther on April 28, 2004. ... One of several fish ladders located at Bonneville Dam on the Columbia River, here looking down the approximately 60 1-foot steps of the ladder. Photographed by Eric Guinther on April 28, 2004. ... Bonneville Lock and Dam is several dam structures that together complete a span of the Columbia River between the US states of Oregon and Washington at River Mile 146. ... Columbia River Gorge, Washington or North side The Columbia River is a river situated in British Columbia and the Pacific Northwest of the United States. ... Scrivener Dam, in Canberra, Australia, was engineered to withstand a once-in-5000-years flood event A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. ... The bridge and weir mechanism at Sturminster Newton on the River Stour, Dorset. ... Many types of fish undertake migrations on a regular basis, on time scales ranging from daily to annual, and with distances ranging from a few meters to thousands of kilometers. ... A ladder A ladder is a vertical set of steps. ...


History of fishways

Written reports of rough fishways date to 17th Century France where bundles of branches were used to create steps in steep channels to bypass obstructions. In 185254, the Ballisodare Fish Pass was constructed in County Sligo, Ireland, to draw salmon into a river that previously did not support a fishery. (16th century - 17th century - 18th century - more centuries) As a means of recording the passage of time, the 17th century was that century which lasted from 1601-1700. ... 1852 was a leap year starting on Thursday (see link for calendar). ... 1854 was a common year starting on Sunday (see link for calendar). ... Sligo (Sligeach in Irish) is a county in the province of Connacht in the west of Ireland. ... The Chinook or King Salmon is the largest salmon in North America and can grow up to 58 long and 126 pounds. ...


As the Industrial Age advanced, dams and other river obstructions became larger and more common, leading to the need for more efficient fishways. Industrialisation (or industrialization) or an industrial revolution (in general, with lowercase letters) is a process of social and economic change whereby a human society is transformed from a pre-industrial to an industrial state . ...

John Day Dam fish ladder view from the Washington (north) side of the Columbia River.
John Day Dam fish ladder view from the Washington (north) side of the Columbia River.

Image File history File links JhnDyDam2. ... Image File history File links JhnDyDam2. ...

Types of fishways

There are five primary types of fishways:

  • Rock Ramp Fishway
  • Pool and Weir
  • Vertical Slot Fish Passage
  • Denil Fishway
  • Fish Elevator
See also: Eel Ladder, Fish migration
Denil Fishway on Salmon Creek (Montana)
Denil Fishway on Salmon Creek (Montana)




An eel ladder is type of fish ladder designed to help eels swim past barriers, such as dams and weirs or even natural barriers, to reach upriver feeding grounds. ... Many types of fish undertake migrations on a regular basis, on time scales ranging from daily to annual, and with distances ranging from a few meters to thousands of kilometers. ... Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... Official language(s) English Capital Helena Largest city Billings Area  - Total  - Width  - Length  - % water  - Latitude  - Longitude Ranked 4th 381,156 km² 410 km 1,015 km 1 44°26 N to 49° N 104°2 W to 116°2 W Population  - Total (2000)  - Density Ranked 44th 902,195 2. ...


A rock-ramp fishway uses large rocks and timbers to create pools and small falls that mimic natural structures. Because of the length of the channel needed for the ladder, such structures are most appropriate for relatively short barriers.


A pool and weir is one of the oldest styles of fish ladders. It uses a series of small dams and pools of regular length to create a long, sloping channel for fish to travel around the obstruction. Effectively, the channel acts as a fixed lock to gradually step down the water level; to head upstream, fish must jump over from box to box in the ladder. Canal locks in England. ...


A vertical slot fish passage is similar to a pool and weir system except that each "dam" has a narrow slot in it near the channel wall. This allows fish to swim upstream without having to leap over an obstacle. Vertical slot fish passages also tend to handle reasonably well seasonal fluctuation in water levels on either side of the barrier.


A Denil fishway uses a series of symmetrical close-spaced baffles in a channel to redirect the flow of water, allowing fish to swim around the barrier. Denil fishways need not have resting areas, although pools can be included in one to provide a resting area or to help reduce the velocity of the flow. Such fishways can be built with switchbacks to minimize the space needed for their construction. A nearly 180-degree turn in a road, trail, or ramp is called a hairpin turn (also hairpin bend or, if in a trail, a switchback). ...


The original design for a Denil fishway was developed in 1909 by a Belgian scientist, G. Denil, but it has been adjusted and adapted in many ways since then. The Alaska Steeppass, for example, is a modular prefabricated Denil fishway variant originally designed for remote areas of Alaska. Official language(s) English Capital Juneau Largest city Anchorage Area  - Total  - Width  - Length  - % water  - Latitude  - Longitude Ranked 1st 663,267 mi² / 1 717 854 km² 808 mi / 1300 km 1,479 mi / 2380 km 13. ...


As its name implies, a fish elevator or fish lift breaks with the ladder design by providing a sort of elevator to carry fish over a barrier. They are well suited to tall barriers. With a fish elevator, fish swim into a collection area at the base of the obstruction. When enough fish accumulate in the collection area, they are nudged into a hopper that carries them into a flume that empties into the river above the barrier. A modern elevator has buttons to allow passengers to select the desired floor. ...

FERC Fish Ladder Safety Sign
Enlarge
FERC Fish Ladder Safety Sign

On the Connecticut River in Holyoke, Massachusetts, for example, a fish elevator lifts up to 500 fish at a time 52 ft (15.85 m) to clear the Holyoke Dam. In its first year of operation (1955), the Holyoke fish elevator carried 4,899 shad over the dam; by 2004, the typical annual number of fish lifted had risen to more than 500,000. Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... The Federal Energy Regulatory Commission (FERC) is the United States federal agency with jurisdiction over interstate electricity sales, wholesale electric rates, hydroelectric licensing, natural gas pricing, and oil pipeline rates. ... The Connecticut River as seen from the French King Bridge in western Massachusetts. ... Holyoke is a city located in Hampden County, Massachusetts, on the banks of the Connecticut River. ... A foot (plural: feet) is a non-SI unit of distance or length, measuring around a third of a meter. ... The metre (Commonwealth English) or meter (American English) (symbol: m) is the SI base unit of length. ... Species (Caspian shad) (Caspian anadromous shad) (Alewife) (American or Atlantic shad) (Persian Gulf shad) many others The shads or river herrings comprise the genus Alosa, fishes related to herring in the family Clupeidae. ...


External links

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Wikimedia Commons has media related to:
Fish ladders
  • A study of the hydraulics of flow over fishways
  • Construction of a vertical slot fish passage and eel ladder for the St. Ours Dam (Richelieu River, Québec)

  Results from FactBites:
 
DNR - Berrien Springs Fish Ladder (246 words)
It is the first dam that fish need to negotiate a ladder to continue their upstream migration.
Competed in 1975 at a cost of $692,500, it was the 2nd major fish ladder completed in the state after the completion of the 6th Street Dam fish ladder on the Grand River in Grand Rapids, Michigan.
This is the only ladder on the St. Joseph River that is a pool-weir since it allows for a sea lamprey barrier in its design.
  More results at FactBites »

 
 

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