Fish passage

Fish passage refers to the ability to effectively and efficiently allow fish to move through a water system, including successfully navigating human-made structures like dams and culverts, which can impede their journey. Whether fish need to migrate 10 miles or 1,000 miles, all fish species need to be able to move throughout water systems to access different habitats, food, and environments that support their life cycles. Fish passage technologies and approaches—such as fish ladders—play a critical role in maintaining sustainable fish populations and healthy aquatic ecosystems.

Dams, culverts, and other human-made structures on rivers and streams provide valuable services—for example hydropower dams may provide flood mitigation, water for drinking and irrigation, and clean renewable power. In 2021, hydroelectric power sources generated about 6 per cent of total electricity generated in the United States, representing about 31 per cent of U.S. renewable energy, and pumped storage hydropower provided approximately 93 per cent of utility-scale energy stored in the U.S. These numbers could increase in the future as reliance on renewable sources of energy continues to grow.

Incorporating fish passage technologies and approaches with hydroelectric dams and other human-made river structures can support river connectivity and help fish navigate these barriers. That’s why multiple pieces of state and federal legislation support fish passage efforts, and the science of fish passage is an active area of research. 

Some fish species, like salmon, migrate significant distances during their lives—traveling from the rivers and streams where they are born, to the ocean where food is abundant, and then back to freshwater spawning locations as adults. Other species—like walleye—migrate completely within freshwater systems to access seasonal habitats and food. Systems with multiple dams may have significant effects on fish species that travel long distances, especially if the dams do not have fish passage structures. Culverts, which carry water under structures such as roads, are smaller than dams but can also reduce or eliminate river connectivity and block fish movements and migrations. For thousands of years, indigenous peoples in the United States relied on fish—including salmon, lamprey, shad, and sturgeon—as key food sources with cultural and spiritual significance. The construction of large dams in the 20th century altered fish habitats and migration routes, making fish passage efforts critical to the sustainability of many fish species and the communities that rely on them. Multiple major dams were built without fish passage options, which made much of the historical habitat of migratory fish species inaccessible and spurred advocacy efforts by Tribes and conservation groups to bring concerns for fish to the forefront

Even though some state legislation supported fish passage as early as 1890, not all dams designed and built during the 20thcentury were required to include fish passage. Fish passage efforts became part of federal legislation with the passage of the Federal Power Act in 1920, and multiple pieces of legislation since then have further supported fish passage in various ways, including the Endangered Species Act in 1973 and the Northwest Power Act in 1980. Federal agencies that manage hydropower dams are now required to mitigate impacts on fish and wildlife.

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