I 



probably excludes extensive mortality of these species. The study by 

 Refield (1961) of the acid dumping grounds confirmed that the effects of 

 acid waste disposal on fish populations and benthic organisms were in- 

 significant. 



Of the bottom-dwelling finfishes sampled by SHL in the Bight only a 

 small number of flounder collected from the sewage dumping area had black 

 ened gills. In laboratory experiments by SHL, two winter flounder were 

 kept in aquaria, one containing a substrate of sludge and the other a 

 substrate of clean sand. A blackening of the gills occurred in the fish 

 held in the aquarium with the sludge substrate, but the significance of 

 this coloration was not established. 



Parasitic organisms were found by SHL in some species of flounder. 

 Tapeworms were common in yellowtail flounder ranging in incidence from 

 7 to 32 percent. The incidence of tapeworms in the yellowtail flounder 

 at stations outside the dumping grounds was about four times greater 

 than in fish collected at the center of the sewage dump where tapeworm 

 infestation had the lowest value (7 percent). No particular pattern 

 is evident from this investigation linking ocean dumping to tapeworm 

 incidence in flounder. No literature was found which describes normal 

 levels of tapeworm infestation in the yellowtail flounder, but flounders 

 generally have a rich parasite fauna. Polyanskii (1955) reported the 

 incidence of the tapeworm Scolex polymorphus in the common dab ( Limanda 

 Limanda) from the Barents Sea to be 25 percent. The chief intermediate 

 hosts for many of the parasites are amphipods which occur in low numbers 

 in the sewage sludge beds and surrounding areas. This may account for 

 the lower incidence of tapeworm infestation. 



Incidence of diseases such as fin-rot in bottom-dwelling finfishes 

 was linked by SHL to waste disposal and associated pathogenic bacteria. 

 This conclusion, however, cannot be fully substantiated, because the 

 study did not identify nor measure the prevalence of pathogenic bacteria 

 in the Bight. Besides, other causes of fin-rot disease have been 

 mentioned in the literature, including high concentrations of mercury. 

 According to Jeffries (1968) , fin-rot infection can be caused simply by 

 restricting the movement of the fish. Fin-rot is often observed in fin- 

 fishes living in unpolluted marine environments. The SHL studies of 

 pathogenic anomalies produced in finfish by sewage sludge were similarly 

 questioned by the SAC. The inadequacy of the experimental design and 

 consequent lack of adequate controls precluded the possibility of 

 statistical analysis of the SHL data. The SAC therefore suggested that 

 further investigation will be required to establish definitely the 

 incidence of fin-rot and the greater uptake of heavy metals by finfish 

 exposed to the sewage sludge. 



It would be hasty to conclude, on the basis of present knowledge, that 

 ocean dumping has had adverse effects on fish populations of the Bight. 

 Introduction of possible toxic substances, such as heavy metals and com- 

 plex hydrocarbons, is certainly undesirable, but long-term effects of 

 such materials on fish are still unknown. 



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