250 



DRAFT 



comparable studies that examine changes in "predation rates on salmonids". The 

 authors conclusion appears to be unsubstantiated. 



Harbor Seals (pape 107-108) 



The report refers several times to Chapman et al. (1991) as a reference source for 

 harbor seal abundance estimates. This reference is a PNUCC report on Snake River 

 Chinook, and is only an indirect reference for harbor seal abundance or population 

 increases in the Columbia River area, Washington, or Oregon. The primai7 source of 

 this information is ODFW, WDW, and NMFS (contract reports, administrative 

 reports, and unpublished data). Some of the abundance estimates presented in this 

 discussion are incoirect. 



The report references Olesiuk et al. (1990) in discussions of harbor seal predation on 

 salmonids, but some of the information and conclusions from this study are omitted. 

 For example, Olesuik et al. (1990) reported that the dominant seal prey items in British 

 Columbia were hake and herring; 75% of the total diet combined. Salmonids made up 

 just four percent of the diet and represented less than three percent of the mean annual 

 escapement for the entire Strait of Georgia. This level of predation loss does not seem 

 to be a highly significant contribution to salmon mortality, even though "predator" 

 numbers apparenUy increased from 10,000 in 1970 to over 80,000 in 1988. 



Using the information from Olesiuk et al. (1990), and the same questionable methods 

 of calculation found in this section, it could be hypothesized that if it took 80,000 seals 

 in B.C. to consume 866,800 pounds of salmon, then the 10,000 seals in Oregon would 

 take only one-eighth of that amount or just 108,350 pounds (12,312 salmon). This 

 estimate represents only three percent of the 1990 Oregon salmon landings (as 

 presented in the report) not 58 percent as suggested (page 108), or just six percent by 

 weight, not 64 percent. 



"Harvey calculated that salmon represented almost 11 percent of the 

 total biomass that harbor seals consumed. " 



The report referred to several Oregon studies that reported that salmonids can comprise 

 between one and 12 percent of seal diets. The report then used a relatively high value 

 of 1 1 percent (Harvey 1988) to complete statewide calculations of salmonid 

 consumption. Not surprisingly, this analysis resulted in a greater estimate than would 

 have been derived by using a median value of salmonid consumption from the various 

 studies. 



A-44 



