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DRAFT 



management activities. However, no information is presented to provide a basis to 

 evaluate the importance of these events. There are several clarifications that should be 

 included in the report: 



(1) the report implies that El Niiio events are relatively common in Oregon. In 

 actuality, El Nino's of the magnitude to bring warm oceanic currents to the 

 coast of Oregon are relatively rare: in the past fifty years this has only occurred 

 four times (1941, 1957-58, 1982-83 and 1992). 



(2) the report does not acknowledge that oceanic events, such as El Nino, can 

 affect salmonid species at differential rates due to differences in offshore 

 migration patterns. For example, north-migrating chinook and steelhead are 

 affected differentiy than Oregon coho or south-migrating chinook stocks. 



2.3.2. Predation and Competition 



This section discusses the potential impact on anadromous salmonids from predation 

 and competition with other wildlife such as marine mammals, birds and other fish 

 species. Estimates of marine mammal predation and competition were based on 

 questionable analytical methods. The information presented in this section was not 

 adequate to evaluate the relative contribution of these inter-specific relationships to the 

 decline of salmonids. The following problems were identified during the review: 



(1) the report fails to recognize that most of the inter-specific relationships 

 discussed are natural occurrences (with the exception of American shad 

 establishment), and that the relative importance of predation and competition is 

 likely influenced by human activities. For example, decreases in salmonid 

 abundance due to other factors such as harvest and habitat degradation result in 



■^ natural losses (predation and competition) becoming increasingly more 

 significant. In addition, no evidence was presented to indicate that such 

 interactions have increased above natural historic levels. 



(2) the discussion of fish predation on juvenile salmonids is restricted to studies 

 of the Columbia River where dam presence has a direct influence on predator- 

 prey relationships. Similar predation rates are questionable for other watersheds 

 in Oregon. However, the evaluation of the importance of this factor to the 

 decline of salmonids does not recognize this regional variation. 



(3) squawfish predation estimates are extracted from one study that may have 

 over-estimated predation rates due to sampling design problems, and another 

 study that estimated squawfish predation in the immediate vicinity of 

 hydroelectric dams where the predation rates observed are much higher than the 

 rest of the squawfish population. 



(4) the discussion of competitive interactions with shad in the Columbia River is 

 largely a hypothesis that is not substantiated by scientific research. The analysis 

 fails to document the extent of spatial and temporal over-lap in estuary rearing 

 habitat between juvenile shad and salmonids, and does not document whether 

 food availability is limiting juvenile salmonid production within Oregon's 

 estuaries. Interestingly, the report also does not note that juvenile shad are a 

 prey source of juvenile salmonids in rivers and estuaries (Emmett et al. 1991). 



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