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information and the primary means available for assessing the 

 combined effects of all actions. 



NMFS has concluded that the three life-cycle models are oest used 

 to provide long-term projections of the relative change in 

 population abundance that may occur as a result of measures 

 imDiemented to reduce mortality, and are less reliable in 

 providing measures of aosoiute abundance. :JMFS wouid therefore 

 use measures of the relative change in expected escapement 

 orovided by the models in evaluating the results of the combined- 

 effects analysis. The relative change in escapement predicted by 

 the life cycle models would be expressed as a benefit ratio. The 

 benefit ratio wouid be calculated using the average escapements 

 from the last five years of the analysis period (2004-2008) from 

 model runs depicting proposed and base period conditions 'benefit 

 ratio = proposed action escapement/base condition escapement) . 

 The benefit" ratio would be used to determine whether all 

 mortality reductions comcined are sufficient to stabilize the 

 listed populations. Although the combined-effects analysis uses 

 the extended fcur life cycle time frame for measuring response, 

 it should be emphasized that the question oeing addressed is 

 whether improvements made in 1993 are sufficient (assuming that 

 those improvements are continued) to halt the declining trend and 

 stabilize the population abundance at specified levels. The 

 combined- effects analysis is therefore an improved method of 

 evaluating improvements made in 1993 and complements the base 

 period analysis described above. 



If the combined- effects analysis does not demonstrate a 

 likelihood of population stability in four life cycles, NMFS will 

 reconsider each proposed agency action and determine wnich 

 actions will be required to provide further reductions in 

 mortality. Determinations from this review of actions will be 

 based on" considerations used in 1992 consultation analyses. 



There are two issues with respect to the combined-effects 

 analysis that merit further explanation. First, is it reasonable 

 to conclude that a stable abundance will result in the continued 

 existence of the species? The second question that needs to be 

 answered is how the benefit ratios developed from the life cycle 

 models will be evaluated. 



Sufficiency of the Stability Criterion 



The proposed criterion for the combined-effects analysis is to 

 stabilize the abundance of the listed species at the levels 

 observed during the 1986-1990 base period. Because of the time 

 lag between actions taken to improve survival in early life 

 history stages and increases in adult abundance, meeting the goal 

 exactly by 2008 would mean that there would be an expectation 

 that the population abundance wouid continue to decline for a 



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