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DRAFT 



(5) estimates of marine mammal predation on salmonids are based upon 

 "simple" mathematical calculations that do not adequately reflect the complexity 

 of predator-prey relationships. In addition, these calculations are based on 

 questionable assumptions, incorrect estimates of marine mammal abundance and 

 population structure, and highly variable information. The variability of these 

 estimates makes direct comparisons to fish harvest questionable. 



(6) the estimates of marine mammal predation are largely extracted from studies 

 of the Columbia River estuary and the Strait of Georgia (British Columbia) 

 where salmonids were concentrated or available during a large portion of the 

 year. These studies cannot be applied to estimate salmonid consumption by 

 Oregon marine mammal populations over a broad geographic area. In addition, 

 calculations of marine mammal predation often assumed that salmonids were 

 available for 365 days of the year: this assumption is not accurate for Oregon. 



CRITIQUE OF METHODS USED TO FORMULATE RECOMMENDATIONS 



The most important part of the OFIC report is the ranking of the relative importance of 

 a variety of management and environmental factors to the decline and lack of recovery 

 of Oregon's anadromous salmonids. This information could provide the basis for 

 prioritizing management efforts to facilitate the recovery of these populations. The 

 importance of the document is, therefore, largely dependent upon the validity of this 

 analysis. 



The Department reviewed the methods used to rank the relative importance of the 

 environmental and maiuigement factors, and assessed the validity of the conclusions 

 derived from this analysis. The methodology employed to rank the factors may be best 

 chara(;terized by the following text from the report: 



'Two separate subjective methods were used to rank relative mortality: rough 

 increased mortality associated with factors studied and a matrix approach. 

 Tables R-1 and R-2 reflect those ratings. " 



Our review of Tables R-1 and R-2 indicated that these analyses were not based on 

 empirical data. Table R-1 was created by an independent subjective ranking of the 

 factors by the authors. Table R-2 was compiled using a matrix analysis approach 

 (Table 2.3-1) but was also largely subjective. The fundamental problems with the 

 authors matrix analysis methodology were: (1) the analysis was not stratified by 

 location and species, (2) the impact of the factors were arbitrarily ranked, (3) some 

 population impacts were redundant and were multiple measures of the same effect on 

 salmonid populations, (4) the measure of a factors impact was arbitrary and was not 

 based on a change in salmonid population abundance, and (S) the method used could 

 not measure the impact of multiple factors acting simultaneously on a population. A 

 discussion of these specific problems follows: 



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