55 



for that week. 



Monitoring Results 



Between May 10 and June 17, a total of 188,526 juvenile salmonids 

 were examined externally for signs of GBD. A total of 138 fish 

 or 0.07% exhibited external signs. Table 1 provides a siiamiary of 

 external sign data by sample method. 



Table 1. External sings of GBD in juvenile salmonids by 

 sample method. Affected fish exhibited at least one 

 cutaneous gas bubble. 



Sample Mode 



Snake R. SMP^ 



Col. R. SMP 



SMP Separator 



FGE^ 



River Reach 



Total 188,526 138 • 0.07 



^ SMP refers to the Smolt Monitoring Program. 



^ Fish Guidance Efficiency (FGE) testing. Of the 30 fish 



affected, 77% were coho observed at The Dalles Dam on May 



15. 



Internal signs were observed in 973 (40.8%) of 2,387 hatchery 

 steelhead examined between May 13 and June 21. See Table 2 for a 

 breakdown of signs observed by location. These internal signs 

 were predominately of low severity and of questionable relevance. 

 A working group of experts on gas bubble disease met in Seattle 

 on June 21, 1994. Several members of this group (who had earlier 

 inspected the gas monitoring program and data) expressed the 

 concern that the internal lateral line and the internal signs 

 (gas bladder, kidney) data were not very useful for determining 

 the prevalence or severity of GBD. They also indicated that the 

 gill filament data, while important for determining impacts of 

 elevated TDG on juvenile salmonids, were useful only if the 

 examination technique was improved aind made consistent among 

 mpnitoring sites. 



