Fish species are affected by the development and operation of dams. Dams without adequate fish passage systems block migrating up stream adults from reaching critical habitat. For downstream juveniles, a substantial proportion can be killed while migrating through dams, both directly through collisions with structures and abrupt pressure changes during passage through turbines and spillways, and indirectly, through non-fatal injury and disorientation. Dams also cause increased travel times for juveniles to migrate downstream due to disruption of natural flowing rivers. This increase travel time and/or migration delay, presents an array of potential survival hazards including increased exposure to predation and disease, depleting energy reserves, and potentially causing metabolic problems associated with smoltification.
The effects of dams and other barriers on fish and wildlife are unquestionably great. Along the west coast of the U.S., there are currently 27 different Endangered Species Act listed Endangered and/or Threatened species. In the Columbia, Snake and Willamette River basins alone there are 12 Endangered and/or Threatened species of migratory salmon. Dams, among other factors, have been one of the leading causes of disruption of returning salmon to their native habitat and disruption of migrating juveniles to the ocean leading to severe declines in runs and even extinction of species.
Currently, upstream adult passage is well-known in the United States and Europe. These systems include fish ladders, fish lifts, locks, and trap & haul programs that capture and truck fish past barriers for release back in-stream. The problem is that even though upstream passage systems are well-known, they do not exist on a majority of dams or provide passage around other barriers and they tend to be very costly.
Additionally, what is not well developed anywhere in the country are upstream solutions that focus on more than the few actual species that passage systems are built to address. On the West Coast of the United States, the vast majority of upstream passage is focused on returning salmon species. There are limited passage systems for other species like the pacific lamprey and none for sturgeon, bull trout, Steelhead returning down-stream or any of the other multiple native regional species. These same issues persist on the East Coast of the U.S. as well with species such as the American Eel, American Shad, native herring, and native Atlantic salmon.
 Supplemental Comprehensive Analysis of the Federal Columbia River Power System and Mainstem Effects of the Upper Snake and other Tributary Actions , NOAA Fisheries May 5, 2008.
 See National Wildlife Federation et al vs. the National Marine Fisheries Service,et al , CV 01-640-RE (Lead Case) 2005 U.S. Dist.Lexis 16345, whereby Judge Redden enumerates the listed species as Upper Columbia River Spring Chinook Salmon, Upper Columbia River Steelhead, Mid-Columbia River Steelhead, Snake River Spring/Summer Chinook Salmon, Snake River Fall Chinook Salmon, SnakeRiver Sockeye Salmon, Snake River Steelhead, Lower Columbia River Chinook Salmon, Lower Columbia River Steelhead, Columbia River Chum Salmon, Upper Willamette River Chinook Salmon, and Upper Willamette River Steelhead.