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causes of Chinook salmon mortality for each life stage, convert 

 that mortality to adult equivalents, and specify the exact 

 reduction in mortality necessary for each action to ensure that 

 the totality of actions does not reduce appreciably the 

 likelihood of the survival and recovery of listed species. 

 Unfortunately, the available scientific information does not 

 provide much certainty in these areas, except that it is clear 

 that substantial reductions in total human- induced mortality are 

 necessary to prevent further decline in the species. However, 

 even if the science were sufficiently developed to identify all 

 the human- induced causes of mortality, it would still be 

 necessary to make judgments about how to apportion the required 

 reductions among life stages and actions. The combined-effects 

 analysis described below is an initial attempt to assess whether 

 the proposed reductions in total mortality for all actions will 

 be sufficient to stabilize the populations abundance, but does 

 not provide any direct guidance on evaluating a specific action. 



Uiven the available information and resulting scientific 

 uncertainty, and the different options for allocating reductions, 

 NMFS must rely on the best available scientific information, on 

 its best professional judgement as to what alternative measures 

 are available and their effectiveness in achieving additional 

 mortality reductions, and on a rule of reason in evaluating 

 actions. 



As an initial matter, there is evidence that actions in each of 

 the four areas (harvest, hatcheries, hydropower and habitat) 

 cause human- induced mortality that has contributed to population 

 declines or is impeding recovery. Because each action has 

 contributed to decline or is impeding recovery, it is reasonable 

 to require that each action demonstrate a reduction in mortality 

 relative to that observed during the base period. The degree of 

 reduction required by each action would depend on a number of 

 factors discussed below. 



There is a great deal of information already available regarding 

 the magnitude and causes of mortality for some actions, 

 particularly harvest and hydropower operations. There is also 

 information on measures that could be taken to reduce mortality 

 for these actions. Existing scientific literature and reports 

 developed by NMFS and other interested parties describe 

 significant sources of mortality and provide recommendations 

 regarding methods for reducing mortality. During the 

 consultation process, measures proposed for each action will be 

 evaluated based on the best available scientific information. 

 NMFS recognizes that some adverse effects on species' survival, 

 as well as the effects of some mitigating measures, are not 

 easily quantifiable. This is particularly true for hatchery 

 actions and actions affecting habitat. The effects are real, 

 however, and will be considered to the extent allowed by the best 

 scientific knowledge and judgment. 



