A few weeks earlier, sledgehammers pounded the Seltzer Dam near Redding in northern California. Similar scenes are occurring along other creeks. Since early last century, dams have controlled river flooding, provided irrigation, and created electricity in many states, particularly in the West. But environmental advocates say that the current dismantling of some dams will restore the vitality of long-declining river ecosystems. For decades, dams have contributed to the rapid depletion of anadromous fish populations from coast to coast.
Dams interrupt the natural rhythm of fish life cycles as they swim from river to ocean and back.
But the odds are stacked heavily against their return. Some salmon species swim hundreds or even thousands of miles to return home. Only a tiny fraction of adult fish ever reach their spawning grounds. Since salmon don' t feed once they leave the ocean, many die from lack of stored body fat. Many others are caught in fishing nets or by a variety of predators.