Editing Fish ladder (section)

==Effectiveness==
[[File:Fish using a fish ladder in Akerselva, Oslo, Norway.jpg|thumb|This fish failed to enter the narrow opening in the fish ladder in [[Akerselva]], 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.<ref name="BlockedMigration">{{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}}</ref> 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.<ref name="UpstreamBattle">{{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}}</ref> Fish passages do not always work.
In practice a challenge is matching swimming performance data to hydrodynamic measurements.<ref name="Katopodis2016">{{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 }}</ref><ref name="Wang2017b">{{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 }}</ref> 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.