result in an increased chance of systemic bacterial 

 infection from foci of infection in devitalized areas 

 of the gut. 



Although the sample size is small, data from 

 this experiment indicate that several aspects of the 

 pathogenesis of GBD need further investigation. A 

 study of factors contributing to the acute death of 

 fish through blockage of the circulatory system by 

 gas emboli is needed to determine if proposed per- 

 missible supersaturation levels will assure survival 

 of fish concurrently stressed by multiple factors. 

 A second study designed to investigate disease 

 susceptibility in fish surviving sublethal supersatu- 

 ration levels is needed. Vibriosis, a septisemic 

 bacterial disease of salmon, is present within the 

 saltwater estuaries of the Oregon Coast and may 

 cause high mortalities in salmonid fish (Cisar and 

 Fryer, 1969). Present knowledge indicates that this 

 disease invades the fish through the gastrointestinal 

 tract. If the integrity of the gastrointestinal tract 

 is significantly disturbed by sublethal supersatura- 

 tion levels, vibriosis or other fish pathogens may 

 cause increased losses. 



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Pathogenesis of Gas Bubble Disease 71 



