FISHERY BULLETIN: VOL. 76, NO. 4 



effect relationship has not yet been de- 

 monstrated for most of these diseases. 



5. Among the most severe and persistent prob- 

 lems in establishing pollutant-disease rela- 

 tionships are: the absence of baseline in- 

 formation about the organisms and their 

 habitats prior to pollution, the existence of 

 multiple pollutants in many badly degraded 

 waters, and the circumstantial nature of 

 much of the evidence linking pollution and 

 disease. 



6. A number of viruses have been found in crus- 

 taceans and molluscs in recent years, and the 

 pathogenic role of two of them (shrimp 

 Baculovirus and oyster Herpesvirus) has 

 been demonstrated by exposure to increasing 

 environmental stress. Other latent virus in- 

 fections of invertebrates may be identified by 

 similar experimental methods. 



The evidence for an association of pollution and 

 disease presented in this paper (except for results 

 of experimental studies) is largely circumstantial. 

 When confronted with the hard question "Can you 

 state positively that the disease condition seen in 

 natural populations is caused by specific environ- 

 mental contaminants?", the answer at present has 

 to be "No." However, the weight of this cir- 

 cumstantial evidence, particularly for diseases 

 such as fin erosion and ulcers, is such that it leads 

 to the conclusion that associations do exist be- 

 tween pollutants and disease. 



ACKNOWLEDGMENTS 



A number of people read drafts of this paper, and 

 many changes and additions have resulted from 

 their comments. I would like to acknowledge the 

 assistance of R. Overstreet, A. Sparks, M. Sher- 

 wood, R. Wolke, J. Couch, J. Pearce, A. Farley, A. 

 Rosenfield, and R. Murchelano — without neces- 

 sarily implying their agreement with any or all of 

 the interpretations and conclusions in this paper. I 

 would also like to thank K. Melkers for maintain- 

 ing the continuity and accuracy of the manuscript 

 through a series of revisions. 



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