Recommendation to Study Effects of Load Following on Juvenile Salmon Migratory Behavior and Survival

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The ISAB recommends to the Council, NOAA Fisheries, and CRITFC that during 2005 there be a study of the effects of load following (flow interruption) on survival of outmigrant smolts in the Snake River and perhaps the lower Columbia River. We understand that there is a new Biological Opinion (BiOp) that bears on flow management, that this new BiOp is being challenged in court, and that there is a specific legal challenge seeking an injunction to increase flow in the Lower Snake River. Any or all of these may constrain the ability to manage flow during the period of outmigration of salmonid smolts this year.Nevertheless, 2005 presents an opportunity to answer critical questions concerning the effects of flow interruption, brought about by load following by the hydrosystem, on survival of migrating juvenile chinook and steelhead during extreme low flow conditions. This critical question is not explicitly discussed in the BiOp or the present challenges to it. The prospects for "no spill" this summer would simplify the design of the experiment. We are sorry that our recommendation comes so late in the season. The timeliness of inspiration cannot always be regulated. Although it is probably too late to include spring chinook and steelhead in the study, and estimating survival of fall chinook with sufficient precision to detect an effect of load flow interruption may be problematic, nevertheless the study should proceed, at least as a pilot study. At the very least it will provide useful information on whether flow fluctuations do or do not affect migratory behavior.

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