Foreword 



We are happy to host the Nitrogen Task Force and 

 other interagency participants of this workshop 

 on gas bubble disease. Six years ago, Battelle first 

 participated in a tripartite research program of the 

 Environmental Protection Agency (EPA), the Na- 

 tional Marine Fisheries Service, and the Atomic 

 Energy Commission involving many of the people 

 here today. One needs only to compare the state of 

 knowledge on gas bubble disease at the time of the 

 tripartite study* with this workshop proceedings 

 in order to fully appreciate the extent to which 

 refinement and accurate delineation of the super- 

 saturation problem has taken place. In 1971, the 

 effects of gas bubble disease seemed to be con- 

 founded with those of other stressors; in the present 

 series of papers, we now see it as a quite lethal factor 

 initiated at a fairly critical level of supersaturation. 

 We also know a good deal about its pathology. With 

 the limited resources available to investigators of 

 gas supersaturation effects, the findings here repre- 

 sent significant accomplishments. 



Several participants have identified areas of 

 uncertainty requiring continuing research during the 

 years ahead. I would like to comment on several 

 points. In listening to the past two days' delibera- 

 tions, I believe that four areas require early atten- 

 tion. They require early attention because data 

 useful in practical applications to minimize gas 

 bubble mortality will depend in a key way on our 

 understanding of the underlying processes. First, it 

 seems to me that determinations are needed of the 

 vertical distributions of fishes with respect to gas 

 supersaturation, especially at periods of high runoff 

 in the river system of the Columbia, for example. To 

 too large an extent, models in use are approxima- 

 tions that need fairly systematic validation for each 

 application. Appropriate field effort, as was de- 



scribed yesterday, is time-consuming and hence 

 expensive when applied to validation purposes. It is 

 also necessary, considering the confoundment 

 caused by possible habitat preferences of fish. 



Second, field effort should be directed to estab- 

 lishing systematically the population pressures and 

 habitat preferences of various fish. Fish seem to 

 have limited ability to distinguish levels or to detect 

 critical levels of gas supersaturation, per se; thus, 

 it is not difficult to see how mortality in salmonids 

 exposed to low levels of gas supersaturation might 

 be greatly aggravated by flight to avoid predation 

 by squawfish, for example. 



Third, pressure-equilibration relationships in 

 fish need to be better defined at physiological levels. 

 We need to keep in mind the experience of hyper- 

 baric physiologists in other fields; namely that tissue 

 gas equilibration, while varying inversely with pres- 

 sure and time, is probably a multi-compartmental 

 process showing widely differing rate constants. 

 Thus, a small compartment, slow in equilibrating, 

 may trigger a neurological incapacitation during 

 decompression even though the body fluids, gener- 

 ally, seem to be equilibrated at the lower pressure. 

 Certain delayed effects, also described in the past 

 two days, may have a similar explanation. 



In the papers and the round table discussions 

 that follow, a number of related ideas are developed. 

 If past progress is a guide, I look forward in our 

 future meetings to definitive explanations of these 

 problems affecting hydroelectric power development. 



Burton E. Vaughan, Manager 



Ecosystems Department 



Battelle, Pacific Northwest Laboratories 



'EPA-Columbia River Thermal Effects Study 

 Vol. 1 - Biological Effects Studies, January 1971 

 Vol. 2 - Temperature Prediction Studies, January 1971 



III 



