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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, ...

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