Notwithstanding the quantity of ink that has been spilt over such questions, only a few things are clear. There was significant over-fishing and habitat disturbance in the Columbia River Basin long before the mainstem dams were built. Snake River populations were depleted to a considerable extent before hydropower development. At the same time, the runs that survived the development of the first half of the century have fared even worse in the second half. The Snake runs of the 1950s were still well above the Endangered Species Act listing threshold. It is surely not fair to ascribe all of the post-1950s decline to hydropower development, but there is little question that hydropower played a very large role. The causes of these declines, however, are "complex and manifold"' and attempts to put a fine point on degrees of fault is likely to do little but keep lawyers happy. B. Early Mitigation The first attempts to address the declines began only a few decades after non-Indian settlement, in the form of fish hatcheries. The rationale for fish hatcheries is primarily social and economic: Habitat degradation is unfortunate but inevitable; mitigation must aim for habitat substitutes; and hatcheries are the substitute.52 In theory, hatcheries compensate for lost habitat by putting salmon eggs into a controlled environment, eliminating the natural forces that limit the number of eggs that hatch and survive in the wild. Hatcheries allow more intense fish harvest because harvesters only have to let enough fish escape to supply eggs for hatcheries, rather than let pass the comparatively large number of adult fish that must spawn in the wild in order to produce self-sustaining populations. It is no wonder, then, that hatcheries took a firm grip on the imaginations of dam builders and fish harvest managers.53 In the dam-building era, the need for mitigation was obvious. Bonneville Dam was equipped with a ladder to allow returning adults to pass the dam, but no provision was made for juvenile fish migrating downstream. Grand Coulee proved to be an even more formidable barrier, and fish and wildlife managers decided that it would be easier to transplant its salmon stocks than Footnotes: 51 National Marine Fisheries Service Snake River Recovery Team, Final Recommendations at p. II-7 (May 1994). 52 Taylor, Making Salmon at 110. 53 Independent Scientific Group, Return to the River at 382.