123 



salmon recovery actions that will address the causes of population 

 decline are most needed.. ;•. 



The criteria for classifying the status of Chinook populations 



in the surveys were chosen to be as single as possible. A 



fundamental requirement was that the criteria be abundance based, 



so that a measure proportionaJ. to sinnuaJ. egg deposition could be 



examined. The criteria shoxild persist in time. Fifteen years was 



selected as the period for the moving average to correspond to 



three generation lengths for the average Chinook population. It 



was felt that processes that were sustained over three generations 



could be viewed as firmly established., and significant, in any 



saJjnon population (see Cuenco et al., in press). The moving 



average used in this application is not sensitive to short term 



fluctuations in abundance. A measure of carrying capacity was seen 



as essential to determining the statias of stocks through time. 



Since only a very crude measure was necessary, it was assxamed that 



the peak annuaJ. survey count would be a minimum estimate of the 



historical carrying capacity of the survey site. Enviro nmen tal. 



degradation continually erodes carrying capacity at most of the 



survey localities, hence current capacity at amy given locality may 



be very much lower than that of the last century. A threshold 



level for determining critical status is also an important measure 



of stock status. As an arbitrary rule, the authors chose seeding 



levels below 50% as a necessary condition indicative of a failing 



stock. Beax in mind that this is a screening technique designed to 



point out potential, not necessarily actual, problems. While it is 



recognized that a healthy salmon stock may frequently fall below 



50% of full seeding, the authors believe that falling below 50% of 



seeding in the presence of a long-term, steady decline waxrants a 



careful examination of stock status. 



Finally, the criteria of stock status need to distinguish 

 populations that are truly at risk of extirpation from populations 

 imdergoing normal fluctuations in abuaadance. The measure of the 

 strength of the linear trend apparent in the annual time series of 

 the fifteen-year moving average appears to be adequate to identify 

 damaged populations, and it gives error bounds for the parameter 

 estimates that permit con^iarisons among localities. The 

 combination of a significant downward trend with less than 50% of 

 seeding in the most recently observed annual abundance pose very 

 con5)elling indications that a population could be badly damaged and 

 decreasing. 



In future research we plan to add the most recent value of the 

 fifteen-year moving average as a percentage of the maximum observed 

 abundance to the list of criteria indicative of a damaged salmon 

 population. A seeding level below 50%, when based on the most 

 recent fifteen-year average, may be sufficient to identify a 

 chronically depressed group of spawners without additional analysis 

 of this kind of data. Vlhen based on only the most recent 

 observation of abundance (e.g. Figs. 1-4, and Table 1) , a seeding 



