Editing Fish ladder (section)

==Types==
{{see also|fish migration}}

;Pool and weir: One of the oldest styles of fish ladders. It uses a series of small dams and pools of regular length to make a long, sloping channel for fish to travel around the obstruction. The channel acts as a fixed [[canal lock|lock]] to gradually step down the water level; to head upstream, fish must jump over from box to box in the ladder.
;Baffle 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. Baffle fishways need not have resting areas, although pools can be included to provide a resting area or to reduce the velocity of the flow. Such fishways can be built with [[hairpin turn|switchbacks]] to minimize the space needed for their construction. Baffles come in variety of designs. The most common design is the Larinier pass, named after the French engineer who designed them. They are suitable for coarse fish as well as salmonids, and can be built large enough to be used by canoes.<ref>{{cite web |url=https://canalrivertrust.org.uk/enjoy-the-waterways/fishing/caring-for-our-fish/how-fish-climb |archive-url=https://web.archive.org/web/20210126222126/https://canalrivertrust.org.uk/enjoy-the-waterways/fishing/caring-for-our-fish/how-fish-climb |archive-date=26 January 2021 |url-status=live |title=How fish climb |publisher=Canal and River Trust |date=22 December 2020}}</ref> The original design for a Denil fishway was developed in 1909 by a Belgian scientist, G. Denil; it has since been adjusted and adapted in many ways. The ''Alaskan Steeppass'', for example, is a modular prefabricated Denil-fishway variant originally designed for remote areas of Alaska. Baffles have been installed by Project Maitai in several waterways in [[Nelson, New Zealand|Nelson]], New Zealand, to improve fish passage as part of general environmental restoration.
;Fish elevator (or fish lift): Breaks with the ladder design by providing a sort of [[elevator]] to carry fish over a barrier. It is 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. On the [[Connecticut River]], for example, two fish elevators lift up to 500 fish at a time, 52 feet (15.85 m), to clear the [[Holyoke Dam]]. In 2013, the elevator carried over 400,000 fish.<ref>{{cite web |title=2013 Connecticut River Migratory Fish
|url=http://www.fws.gov/r5crc/fish/old13.html |website=U.S. Fish and Wildlife Service |publisher=United States Fish and Wildlife Service |access-date=October 25, 2016}}</ref>
;Rock-ramp fishway: Uses large rocks and timbers to make 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. They have a significant advantage in that they can provide fish spawning habitat.<ref>{{cite book |first=Luther P. |last=Aadland |title=Reconnecting Rivers: Natural Channel Design in Dam Removals and Fish Passage |publisher=Minnesota Department of Natural Resources |year=2010 |url=http://www.dnr.state.mn.us/eco/streamhab/reconnecting_rivers.html}}</ref>
;Vertical-slot fish passage: 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 leaping over an obstacle. Vertical-slot fish passages also tend to handle reasonably well the seasonal fluctuation in water levels on each side of the barrier. Recent studies suggest that navigation locks have a potential to be operated as vertical slot fishways to provide increased access for a range of biota, including poor swimmers.<ref>{{cite journal |last1=Silva |first1=S. |last2=Lowry |first2=M. |last3=Macaya-Solis |first3=C. |last4=Byatt |first4=B. |last5=Lucas |first5=M. C. |year=2017 |title=Can navigation locks be used to help migratory fishes with poor swimming performance pass tidal barrages? A test with lampreys |journal=Ecological Engineering |volume=102 |pages=291–302 |doi=10.1016/j.ecoleng.2017.02.027 |doi-access=free |bibcode=2017EcEng.102..291S |url=https://durham-repository.worktribe.com/preview/1363274/21139.pdf }}</ref><ref>{{cite journal |last1=Quaranta |first1=E. |last2=Katopodis |first2=C. |last3=Revelli |first3=R. |last4=Comoglio |first4=C |year=2017 |title=Turbulent flow field comparison and related suitability for fish passage of a standard and a simplified low-gradient vertical slot fishway |journal=River Research and Applications |volume=33 |issue=8 |pages=1295–1305|doi=10.1002/rra.3193 |bibcode=2017RivRA..33.1295Q |s2cid=134135405 |url=https://iris.polito.it/bitstream/11583/2678527/1/Quaranta%20et%20al._final%20version.pdf }}</ref>
;Fish siphon: Allows the pass to be installed parallel to a water course and can be used to link two watercourses. The pass utilises a syphon effect to regulate its flow. This style is particularly favoured to aid flood defence.
;Fish cannon: A wet, flexible pneumatic tube uses air pressure to suck in salmon one at a time and gently shoot them out into the destination water. The system was originally designed by [[Bellevue, Washington]] company Whooshh to safely move apples.<ref>[https://www.youtube.com/watch?v=kICS32kady4 'Salmon Cannon' Fires Fish Over Dams At 22mph] 13 August 2014 ''www.youtube.com'', accessed 15 January 2022</ref><ref>{{cite web |url=https://www.livescience.com/48752-salmon-cannon-fish-spawning.html |title=Whoosh: 'Salmon Cannon' Shoots Fish Upstream to Spawn |date=13 November 2014 |website=www.livescience.com |access-date=16 January 2022}}</ref><ref>{{cite news |url=https://www.theguardian.com/environment/2019/aug/15/salmon-cannon-fish-dam |title=What is the 'salmon cannon' and how do the fish feel about it? |date=15 August 2019 |newspaper=The Guardian |access-date=16 January 2022}}</ref>
;Fish lock: A fish lock is a structure designed to facilitate the passage of fish over barriers such as dams or weirs, enabling them to access upstream habitats essential for spawning and growth. It operates similarly to a navigation lock, using a chamber that fills and empties to move fish across the barrier by adjusting water levels to match the upstream and downstream sections. There are several types of fish locks, such as the Borland fish lock, Deelder lock, Pavlov lock, and most recently, the Fishcon lock.<ref>{{Cite web |title= Fish lock, n. Meanings, etymology and more &#124; Oxford English Dictionary|url=https://www.oed.com/dictionary/fish-lock_n?tl=true}}</ref>
;Fishcon lock: The Fishcon lock enables both upstream and downstream fish migration in a compact space and was developed by the company Fishcon. Between 2019 and mid-2024, seven Fishcon locks were installed in Austria, Germany and Switzerland. Five of these installations have been already independently evaluated with great results and deemed functional according to Austrian and German standards.<ref>{{Cite news |last=Mayrhofer |first=Bernhard |date=2024 |title=First monitoring results and operation experience of a new type of fish pass |url=https://energetykawodna.info/library/2024/06/20/171887479754.pdf |access-date= |work=Energetyka Wodna |pages=44–46 |archive-date=2024-09-25 |archive-url=https://web.archive.org/web/20240925120058/https://energetykawodna.info/library/2024/06/20/171887479754.pdf |url-status=dead }}</ref><ref>{{Cite journal |last=Mayrhofer |first=Bernhard |date=2024 |title=Fishcon-Schleuse ermöglicht Fischauf- und -abstieg |url=https://www.vms-detmold.de/magazin/wasserkraft-energie?srsltid=AfmBOooNzXtb-xLVlOSm1eN9cszlIHjzJ80NURIBzE9Ep7FwN7sE6Blw |journal=Wasserkraft & Energie |volume=3/2024 |pages=29–39}}</ref>
;Borland fish lock: This is similar to a canal lock. At the downstream end of the obstruction, fish are attracted to a collecting pool by an outflow of water through a sluice gate. At fixed intervals, the gate is closed, and water from the upper level fills the collecting pool and an inclined shaft, lifting the fish up to the upstream level. Once the shaft is full, a [[sluice]] at the top level opens, to allow fish to continue their journey upstream. The top sluice then closes, and the shaft empties for the process to begin again. A number of Borland fish locks have been built in Scotland, associated with [[Hydroelectric Dams|hydro-electric dams]], including one at [[Aigas Dam]] on the [[River Beauly]].<ref>{{cite web |last=Wood |first=Emma |year=2005 |title=Power from the Glens |url=http://www.scottish-southern.co.uk/sseinternet/assets/569CABFE-1165-4ED8-9419-CF3B5A64BC98.pdf |archive-url=https://web.archive.org/web/20071018233304/http://www.scottish-southern.co.uk/sseinternet/assets/569CABFE-1165-4ED8-9419-CF3B5A64BC98.pdf |archive-date=18 October 2007 |publisher=Scottish and Southern Energy |page=8}}</ref>
;Deelder lock: Developed by Dutch engineer [[Klaas Deelder]], this design features two chambers separated by an internal [[weir]]. Fish enter the lower chamber, which then fills with water, allowing them to swim over the weir into the upper chamber and continue upstream. This method has been effective in passing a wide range of fish species and sizes.<ref>{{Cite web |last=Harris |first=John |date=November 25, 2024 |title=Passage of non-salmonid fish through a Deelder lock on a lowland river |url=https://www.academia.edu/17718321 |access-date= |website=Academia}}</ref>
;Pavlov lock: This design, attributed to Russian engineer [[Dmitry Sergeyevich Pavlov]], incorporates features to guide fish into the lock chamber, such as attraction flows and holding pools. The lock operates cyclically, filling and emptying to move fish upstream, and has been implemented in various regions to assist [[fish migration]].<ref>{{Cite web |last=Travade(1) Larinier(2) |first=F.(1) Michel(2) |date=October 2002 |title=Fish Locks and fish lifts |url=https://www.researchgate.net/publication/27335346 |access-date= |website=ResearchGate}}</ref>

{{cleanup-gallery|date=April 2025}}
<gallery>
File:John Day Dam fish ladder.jpg|[[John Day Dam]] fish ladder on the [[Columbia River]], United States
File:Fischlift1.jpg|Fish elevator
File:Grave vistrap laag.jpg|Fish ladder in [[Meuse (river)|Meuse River]] the Netherlands
File:CapilanoRiverRegPark-salmonladder.jpg|Fish ladder in [[North Vancouver, British Columbia (district municipality)|North Vancouver]], Canada
File:Climbing Chinook Salmon (15419560541).jpg|[[Chinook salmon]] climbing a ladder
File:Dart at Salmon leap 2.JPG|Detail of fish ladder on the [[River Dart]] in England
File:Salmon Fish Ladder.jpg|Salmon climbing a ladder on [[Issaquah Creek]], [[Washington state|Washington]]
File:Pico Blanco Fish Ladder.jpg|Bi-directional, seasonal ladder at [[Camp Pico Blanco]] on the [[Little Sur River]] in [[Big Sur]], California, United States
File:Laxtrappan.JPG|Fish ladder for [[salmon]] near the power station in [[Gullspång]], [[Sweden]]
File:Fish pass.jpg|A small fish ladder on the [[River Otter, Devon]]
File:Fish ladder entrance at mouth of Mosel River.jpg|Fish ladder access point (from the downriver side of the power generator-lock complex): [[Moselle|Mosel]] at [[Koblenz]]
File:2-Kammern-Organismenwanderhilfe Alm.jpg|Fishcon lock on the river Alm in Austria
</gallery>