247 

 DRAFT 



'Studies by Poe et al. (1991) between 1983 and 1986 revealed that from 

 April to August salmonids comprised (by weight) 67 percent of the diet of 

 northern squawfish, 33 percent of channel c^sh, 14 percent of walleye, 

 and four perceru ofsmallmouth bass. ' 



These results are skewed by disproportionate sampling in the boat-restricted zone (Poe 

 etal. 1991). 



V. Petersen et al. (1990) observed that salmonids constituted from 73 to 

 99 percent (mean 91 percent) of the northern squawfish diet in July of 

 1988. • 



In the immediate vicinity of the dam which is not representative of the squawfish 

 population. 



"However, if northern squawfish prefer dead and injured over healthy 

 prey, then these fish may be more of a scavenger than an active 

 predator. ' 



Clearly an active predator (Rieman et al. 1991): 



1. Most loss occurs far from dams where fish are likely to be healthy. 



2. Laboratory tests not corroborated in field where different conditions make it 



difficult to discern prey condition (by predators). 



Bird Predation (Pages 105-106) 



This section provides some information concerning bird predation on salmonids, 

 however, it does not provide the information necessary to evaluate the relative 

 contribution of this factor to the decline of Oregon's salmonid resources. While it is 

 true that bird predation is a natural component of the freshwater and marine 

 ecosystems, no information was presented to suggest that the loss of salmonids to this 

 factor is increased above natural historic levels. 



Specific comments on the information presented are as follows: 



'Ruggerone (1986) estimated that ring-billed gulls... consumed two 

 percent of the salmon and steelhead trout passing Wanapum Dam. . . " 



Ring-billed gulls, as many gull species, are opportunistic feeders and are likely to 

 exploit prey as the opportunity exists. The predation rates observed by Ruggerone 

 (1986) may not be applicable to the overall gull population, however, as the 

 information was collected in the vicinity of a dam. Salmonids at this location were 



A-41 



