The passage of fingerlings at low-head dams on the Columbia-Snake watershed is a problem of attrition. When all of the low-head dams are completed, the progeny of some of our most important stocks of fish will be forced to pass through either the spillways or the turbines of about 10 low-head dams to reach the sea. The fish that use the spillways enjoy relatively safe passage. When the storage reservoirs are completed, however, nearly all of the water will pass through the turbines, where losses of fish are now estimated at 11%. Such losses at each of 10 dams would seriously deplete the runs and would make perpetuation of important fish stocks impractical.