Later, they built fish hatcheries and installed ladders to allow returning adult salmon to swim past the dams. Still later, the Army Corps of Engineers barged juvenile fish downriver and placed mechanical screens in front of powerhouse intakes to keep fish away from turbines. Yet, by the late 1980s, salmon were becoming extinct. Oregon Sen. Mark Hatfield asked the National Academy of Sciences to appraise the science underlying salmon recovery. In 1995, the Northwest Power Planning Council asked another group of independent scientists to assess the council's salmon program, which had proposed drawing down reservoirs on the lower Snake.
Species are part of ecological communities.
They will do well only if the ecological systems they are part of are working. Technology, no matter how ingenious, is no substitute for a healthy ecosystem. For one thing, they said, we needed to think about the overall structure of salmon populations. For salmon, these were the garden spots, and they became the core of the big, pre-development salmon runs, mainly in the main stem of the Columbia and in the lower stretches of major tributaries. Spawning grounds in higher tributary areas were more spartan.