Fish ladder

File:Denil fish ladder.jpg]]

Written reports of rough fishways date to 17th-century France, where bundles of branches were used to make steps in steep channels to bypass obstructions.

A 1714 construction of an old channel bypassing a dam, "originally cut for the passage of fish up and down the river", is mentioned in the 1823 U.S. Circuit Court Case Tyler v. Wilkinson. This example predates the 1880 fish ladder at Pawtuxet Falls. The 1714 channel "wholly failed for this purpose" and, in 1730, a mill was built in its place. The channel and its mill usage became an important legal case in U.S. water law.{{cite web |last1=Mason |first1=William P. |title=Tyler v. Wilkinson |url=https://opencasebook.org/casebooks/510-open-source-property/resources/3.3.2.2-tyler-v-wilkinson/ |website=Open Casebook |publisher=Harvard Law School Library |access-date=30 August 2023}}

A pool and weir salmon ladder was built around 1830 by James Smith, a Scottish engineer on the River Teith, near Deanston, Perthshire in Scotland. Both the weir and salmon ladder are there today and many subsequent salmon ladders built in Scotland were inspired by it.{{Cite web|url=https://www.gracesguide.co.uk/James_Smith_(1789-1850)|title = James Smith (1789-1850) - Graces Guide}}

A version was patented in 1837 by Richard McFarlan of Bathurst, New Brunswick, Canada, who designed a fishway to bypass a dam at his water-powered lumber mill.Mario Theriault, Great Maritime Inventions 1833–1950, Goose Lane, 2001, p. 45 In 1852–1854, the Ballisodare Fish Pass was built in County Sligo in Ireland to draw salmon into a river that had not supported a fishery. In 1880, the first fish ladder was built in Rhode Island, United States, on the Pawtuxet Falls Dam. The ladder was removed in 1924, when the City of Providence replaced the wood dam with a concrete one. USA legislated fishways in 1888.{{cite web |title=33 U.S. Code § 608 - Construction of fishways |url=https://www.law.cornell.edu/uscode/text/33/608 |website=LII / Legal Information Institute |language=en}}

As the Industrial Age advanced, dams and other river obstructions became larger and more common, leading to the need for effective fish by-passes.Office Of Technology Assessment Washington DC (1995) [https://books.google.com/books?id=ctBsJJ0oKHEC&dq=%22Fish+passage+technologies%22&pg=PA9 Fish passage technologies : protection at hydropower facilities] Diana Publishing, {{ISBN|1-4289-2016-1}}.

{{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 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 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.{{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}} 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, 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.{{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}}

;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.{{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}}

;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.{{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 }}{{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 }}

;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.[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{{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}}{{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}}

;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.{{Cite web |title= Fish lock, n. Meanings, etymology and more | Oxford English Dictionary|url=https://www.oed.com/dictionary/fish-lock_n?tl=true}}

;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.{{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 }}{{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}}

;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 hydro-electric dams, including one at Aigas Dam on the River Beauly.{{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}}

;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.{{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}}

;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.{{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}}

{{cleanup-gallery|date=April 2025}}

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 the Netherlands

File:CapilanoRiverRegPark-salmonladder.jpg|Fish ladder in 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

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): Mosel at Koblenz

File:2-Kammern-Organismenwanderhilfe Alm.jpg|Fishcon lock on the river Alm in Austria

File:Fish using a fish ladder in Akerselva, Oslo, Norway.jpg, Norway]]

Fish ladders have a mixed record of effectiveness. This varies for different types of species, with one study showing that only three percent of American Shad make it through all the fish ladders on the way to their spawning ground.{{cite web|last1=Waldman|first1=John|title=Blocked Migration: Fish Ladders On U.S. Dams Are Not Effective|url=http://e360.yale.edu/feature/blocked_migration_fish_ladders_on_us_dams_are_not_effective/2636/|website=Yale Environment 360|publisher=Yale School of Forestry and Environmental Sciences|access-date=18 March 2016}} Effectiveness depends on the fish species' swimming ability, and how the fish moves up and downstream. A fish passage that is designed to allow fish to pass upstream may not allow passage downstream, for instance.{{cite web|last1=Kraft|first1=Amy |date=February 20, 2013 |title=Upstream Battle: Fishes Shun Modern Dam Passages, Contributing to Population Declines|url=http://www.scientificamerican.com/article/upstream-battle-fishes-shun-modern-dam-passages-population-declines/|website=Scientific American|access-date=18 March 2016}} Fish passages do not always work.

In practice a challenge is matching swimming performance data to hydrodynamic measurements.{{cite journal|last1=Katopodis |first1=C. |last2=Gervais |first2=R. |title= Fish Swimming Performance Database and Analyses |journal=DFO CSAS Research Document No. 2016/002, Canadian Science Advisory Secretariat, Fisheries and Oceans Canada, Ottawa, Canada |pages= 1–550 |year=2016 }}{{cite journal|last1=Wang |first1=H. |last2=Chanson |first2=H. |author-link2=Hubert Chanson |title= How a better understanding of Fish-Hydrodynamics Interactions might enhance upstream fish passage in culverts |url= http://espace.library.uq.edu.au/view/UQ:696033 |journal=Civil Engineering Research Report No. CE162 |pages= 1–43 |year=2017 }} Swim tests rarely use the same protocol and the output is either a single-point measurement or a bulk velocity. In contrast, physical and numerical modelling of fluid flow (i.e. hydrodynamics) deliver a detailed flow map, with a fine spatial and temporal resolution. Regulatory agencies face a difficult task to match hydrodynamic measurements and swimming performance data.

In North Carolina, the Cape Fear River watershed, effectiveness of the fish passageway improves habitual conditions for cleaner water and increase fish population. Cape Fear River uses "lock and dam" structures that prevent fishes from migrating upstream. In 2012, at Lock and Dam No.1, the watershed allows the fish to migrate upstream using a fish passage structure that resembles stream rapids. The Cape Fear River Partnership by NOAA's Office of Habitat Conservation, are using the fish passageways to restore fish back into the water shed to improve the habitat with cleaner water and benefiting local communities.{{Cite web |last=Fisheries |first=NOAA |date=2024-12-17 |title=Reopening Cape Fear River to Migration Benefits Both Fish and People {{!}} NOAA Fisheries |url=https://www.fisheries.noaa.gov/feature-story/reopening-cape-fear-river-migration-benefits-both-fish-and-people |access-date=2025-06-03 |website=NOAA |language=en}}

{{See|Culvert#Fish passage}}

The ecological impact of culverts on natural streams and rivers has been recognised. While the culvert discharge capacity derives from hydrological and hydraulic engineering considerations,{{cite book|author=Chanson, H. |title= The Hydraulics of Open Channel Flow: An Introduction |publisher=Butterworth-Heinemann, 2nd edition, Oxford, UK |year=2004 |isbn= 978-0-7506-5978-9|author-link= Hubert Chanson }} this results often in large velocities in the barrel, which may prevent fish from passing through.

Baffles may be installed along the barrel invert to provide some fish-friendly alternative.{{cite journal |last1=Olsen |first1= A. |last2=Tullis |first2=B. |title= Laboratory Study of Fish Passage and Discharge Capacity in Slip-Lined, Baffled Culverts |journal=Journal of Hydraulic Engineering |volume=139 |issue=4 |pages= 424–432 |issn= 0733-9429 |year=2013 |doi=10.1061/(asce)hy.1943-7900.0000697}}{{cite journal |author-link1=Hubert Chanson |last1=Chanson |first1=H. |last2=Uys |first2=W. |title= Baffle Designs to facilitate Fish Passage in Box Culverts: A Preliminary study |url= https://espace.library.uq.edu.au/view/UQ:396517 |journal=6th IAHR International Symposium on Hydraulic Structures, Hydraulic Structures and Water System Management |pages= 295–304 |doi= 10.15142/T300628160828 |doi-access=free |isbn= 978-1-884575-75-4 |year=2016 }}{{cite book|last1=Cabonce |first1=J. |last2=Fernando |first2=R. |last3=Wang |first3=H. |last4=Chanson |first4=H. |author-link4=Hubert Chanson |title=Using Triangular Baffles to Facilitate Upstream Fish Passage in Box Culverts: Physical Modelling| url= http://espace.library.uq.edu.au/view/UQ:653838 |publisher= Hydraulic Model Report No. CH107/17, School of Civil Engineering, The University of Queensland, Brisbane, Australia, 130 pages |year=2017 |isbn= 978-1-74272-186-6}} For low discharges, the baffles decrease the flow velocity and increase the water depth to facilitate fish passage. At larger discharges, baffles induce lower local velocities and generate recirculation regions. However, baffles can reduce drastically the culvert discharge capacity for a given afflux,{{cite journal|last=Larinier |first=M. |title= Fish Passage through Culverts, Rock Weirs and Estuarine Obstructions |journal=Bulletin Français de la Pêche et de la Pisciculture |volume=364 |issue=18 |pages= 119–134 |year=2002 |doi= 10.1051/kmae/2002097 |doi-access=free |url=https://www.kmae-journal.org/10.1051/kmae/2002097/pdf }} thus increasing substantially the total cost of the culvert structure to achieve the same design discharge and afflux. It is believed that fish-turbulence interplay may facilitate upstream migration, albeit an optimum design must be based upon a careful characterization of both hydrodynamics and fish kinematics.{{cite journal|last1=Wang |first1=H. |last2=Chanson |first2=H. |author-link2=Hubert Chanson |title= Baffle Systems to Facilitate Upstream Fish Passage in Standard Box Culverts: How About Fish-Turbulence Interplay? |url= http://espace.library.uq.edu.au/view/UQ:678859 |journal=37th IAHR World Congress, IAHR & USAINS, Kuala Lumpur, Malaysia |volume=3 |pages= 2586–2595 |year=2017 }}{{cite journal|last1=Wang |first1=H. |last2=Chanson |first2=H. |author-link2=Hubert Chanson |title= Modelling Upstream Fish Passage in Standard Box Culverts: Interplay between Turbulence, Fish Kinematics, and Energetics |journal=River Research and Applications |volume=34|issue=3 |pages= 244–252 |year=2018 |doi=10.1002/rra.3245|url= http://espace.library.uq.edu.au/view/UQ:719818/UQ719818_preprint_OA.pdf |doi-access=free |bibcode=2018RivRA..34..244W }} Finally the practical engineering design implications cannot be ignored, while a solid understanding of turbulence typology is a basic requirement to any successful boundary treatment conducive of upstream fish passage.{{cite journal|last=Chanson |first=H. |author-link=Hubert Chanson |title= Utilising the Boundary Layer to Help Restore the Connectivity of Fish Habitats and Populations. An Engineering Discussion |journal=Ecological Engineering |volume=141|issue=105613 |pages= 105613 |year=2019 |doi=10.1016/j.ecoleng.2019.105613|bibcode=2019EcEng.14105613C |s2cid= 207901913 |url= https://espace.library.uq.edu.au/view/UQ:8e04f63/UQ8e04f63_graphical.pdf}}

Hydropower effects the mitigation of fish that prevents them to live in their habitat. The hydropower plants block fish from mitigating which can injure the species and effect the biodiversity.  Fish passageways are used to replenish the habit. A project in Southwest Washington reopened 117 miles of salmon and steelhead habitat at its hydroelectric dams. To replenish the habitat, it collects fish in the freshwater to the seawater and away from the intake of a dam and releases the fish downstream to allow them to mitigate. Once adults, the fish ladders allow the fish to move further downstream. {{Cite web |title=Fish Passage Systems Enhance Environmental Sustainability |url=https://www.bv.com/projects/fish-passage-systems-enhance-environmental-sustainability |access-date=2025-06-03 |website=www.bv.com |language=en-US}}

The use of nature-like fishways or technical fishways are ways to provide efficient use for fish to move stream. Nature-like fishways are made with natural material to mimic natural waterways with low slopes and flow and large spaces with low heights for species to move. Technical fishways are constructed to allow fish species to move safely in any direction through barriers. Hydropower plants and their dams can use the types of fishways to adapt to fish species movements and provide efficient maintenance. {{Cite journal |last=Karpefors |first=Tea |last2=Quist |first2=Hanna |date=2024 |title=Modular Fish Ladders for Small-scale Hydropower Plants in Sweden |url=http://hdl.handle.net/20.500.12380/308906 |journal=Chalmers ODR}}

• {{anl|Elver pass}}
• {{anl|Glen D. Palmer Dam}}
• {{anl|Fish doorbell}}
• {{anl|Fish migration}}
• {{anl|Fish screen}}
• {{anl|Pitlochry fish ladder}}
• {{anl|Salmon run}}

{{reflist}}

• [https://web.archive.org/web/20110518112904/https://www.nwp.usace.army.mil/pa/docs/pubs/salmon.pdf To Save the Salmon] (1997) US Army Corps of Engineers.
• [http://staff.civil.uq.edu.au/h.chanson/reprints.html#YouTube Fish-friendly waterways and culverts - Integration of hydrodynamics and fish turbulence interplay] (2017) The University of Queensland.

{{commons}}

• [http://herkules.oulu.fi/isbn9514259777/html/index.html A study of the hydraulics of flow over fishways] {{Webarchive|url=https://web.archive.org/web/20041030161007/http://herkules.oulu.fi/isbn9514259777/html/index.html |date=2004-10-30 }}
• [https://web.archive.org/web/20040922074048/http://www.slv2000.qc.ca/divers/parcs_canada/saint_ours_accueil_a.htm Construction of a vertical slot fish passage and eel ladder for the St. Ours Dam] (Richelieu River, Québec)
• [https://www.fpc.org Fish Passage Center]
• [http://www.fao.org/docrep/010/y4454e/y4454e00.htm Fish passes. Design, dimensions and monitoring], Food and Agriculture Organization of the United Nations/Deutscher Verband für Wasserwirtschaft und Kulturbau (DVWK), Rome, 2002 {{ISBN|92-5-104894-0}} {{ISBN|3-89554-027-7}} ([ftp://ftp.fao.org/docrep/fao/010/y4454e/y4454e.zip Zip download]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}} from FTP area of the FAO's European Inland Fisheries Advisory Commission (EIFAC))
• [https://www.washingtonpost.com/wp-dyn/content/article/2007/01/30/AR2007013001757.html U.S. Orders Modification of Klamath River – Dams Removal May Prove More Cost-Effective for allowing the passage of Salmon]—The Washington Post, January 31, 2007
• [https://www.science.org/content/article/fish-ladders-and-elevators-not-working Fish Ladders and Elevators not working.]
• [http://staff.civil.uq.edu.au/h.chanson/fish_culvert.html Upstream fish passage in box culverts: how do fish and turbulence interplay?] by Dr Hang Wang and Professor Hubert Chanson, School of Civil Engineering, University of Queensland

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Category:Aquatic ecology

Category:Ecological connectivity

Category:Fish migrations