Fish Ladders

Fish ladders are designed to allow fish passage around dams or other barriers by providing a series of relatively low steps that the fish may leap from one level to the next (hence the term ladder). Anadromous fish (e.g., salmon, sturgeon, and lamprey) need access to both the rivers where they spawn and the oceans where they spend their adult life. Dams have had such negative impacts on populations of anadromous fish because they fragment the river ecosystem, preventing adults from reaching their spawning grounds. This inability to reproduce has led to the decline or local extinction of many anadromous fish, including numerous species of salmon, steelhead, suckers, and lamprey.

Fish ladders have become the focus of political controversy on at least two counts. Some rivers, such as the Klamath River in California and Oregon, have no fish ladders. Thus fish in this river are totally blocked from habitat upstream of dams. The Klamath was once the third-largest salmon producing stream on the west coast of the United States. The fact that four dams block Spring Chinook salmon from 90 percent of their original spawning ground is cited as a chief reason that fishery is now in a state of collapse.

Fish ladders are also controversial because they are not as effective in creating fish passage as once believed. For example, fish ladders are more successful in allowing the migration of adult salmon swimming upstream to spawn than the juvenile fish who migrate downstream to the ocean. National Marine Fisheries Service reported that Fall Chinook juvenile mortality on the Lower Snake reservoirs could be as high as 20 percent per dam. Even adult migration in fish ladders is imperfect. The study further reported that up to 40 percent of adult fish in the Lower Snake fall back over the dam spillways or pass through the turbines after moving up the fish ladders. These fish are less likely to spawn. With four dams on the Lower Snake and four more on the Columbia the cumulative effect of these dams are problematic for salmon even with fish ladders.

In the Pacific Northwest, salmon are a cultural icon to Native American and other cultures. Native Americans still consume salmon, steelhead, lamprey, and other anadromous fish. The decline in these populations, however, has had significant health, cultural, economic, and social effects for these communities. Furthermore, salmon is the basis of a significant but heavily reduced commercial fishing industry on the west coast. In 2005 the inadequacy of fish ladders had been the basis for the three largest tribes in California demanding removal of four dams on the Klamath River in Oregon and California.

Fish ladders, also work better for some species than others. Lamprey do not travel well in fish ladders either as adults going upstream or as juveniles attempting to reach the ocean. Although they do [Page 678]not have much appeal for non-Native American people, lamprey are an important food source for Native Americans. Pacific lamprey and other lamprey species have been considered for the Endangered Species status.

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