FISHERY BULLETIN: VOL. 76, NO. 4 



from a distant control area ( Dana Point). Wellings 

 et al. (1976) found abnormally high concentra- 

 tions of PCB's in English sole and starry flounders 

 from the Duwamish River in Washington. 



Several authors have postulated that fin erosion 

 in flatfish may be initiated by direct contact of 

 tissues with contaminated sediments. Mearns and 

 Sherwood (1974) and Sherwood and Mearns 

 (1977), for example, suggested that toxic sub- 

 stances (sulfides, heavy metals, chlorinated hy- 

 drocarbons, etc.) could remove or modify the pro- 

 tective mucus coat and expose epithelial tissues to 

 the chemicals. Sherwood and Bendele^ reported 

 that Dover sole from the California coast with 

 severe fin erosion produced much less mucus than 

 normal fish. 



It seems quite likely that the "fin erosion" syn- 

 drome in fish includes chemical stress, possibly 

 acting on mucus and/or epithelium; stress result- 

 ing from marginal dissolved oxygen concentra- 

 tions, possibly enhanced by a sulfide-rich envi- 

 ronment; and secondary bacterial invasion in at 

 least some instances. Some recent experimental 

 information tends to support this hypothesis. 



A series of experiments at the Gulf Breeze (Fla.) 

 Environmental Research Laboratory of the U.S. 

 Environmental Protection Agency, using the spot, 

 resulted in experimental production of fin rot dis- 

 ease following exposure to 3-5 ^tg/l of Aroclor 1254 

 (Couch 1974a). Mortalities of up to 80% were re- 

 ported. 



Minchew and Yarbrough (1977) exposed Mugil 

 cephalus in brackish water ponds ( 12%o) to 4-5 ppm 

 crude oil and found that fin erosion developed in 

 most of the exposed fish within 6-8 days. Lesions 

 were often hemorrhagic, and a tentative Vibrio sp. 

 was isolated consistently from surfaces of diseased 

 fish, but was rarely found systemically. Fin regen- 

 eration characterized most experimental fish 2 

 mo after exposure. This experiment should be re- 

 peated and extended. 



Experimental induction of fin erosion has fol- 

 lowed exposure to several other contaminant 

 chemicals. Chronic exposure of fingerling rainbow 

 trout, Salmo gairdneri, to lead caused a variety of 

 grossly visible abnormalities, including fin ero- 

 sion (Davies and Everhart^); and chronic exposure 

 of minnows (Phoxinus phoxinus) to zinc and cad- 



■'Sherwood, M. J., andR. A. Bendele. 1975. Mucous produc- 

 tion in Dover sole. Annu. rep., Coastal Water Res. Proj., El 

 Segundo, Calif., p. 51. 



8Davies, P. H.,andJ.H. Everhart. 1973. Effects of chemi- 

 cal variations in aquatic environments. III. Lead toxicity to 



mium resulted in similar abnormalities 

 (Bengtsson 1974, 1975). 



A recent report by Overstreet and Howse ( 1977) 

 pointed to fin erosion and other abnormalities as 

 indicators of gradually increasing pollution stress 

 on the Mississippi gulf coast. Among other disease 

 conditions noted by Overstreet and Howse was 

 "red sore," characterized by hemorrhagic lesions 

 beneath scales, occasional hyperplasia, and ac- 

 companying ciliate (Epistylis sp.) infestation of 

 the body surfaces. The authors indicated that red 

 sores now occur in many of the fish in some fresh- 

 water and low salinity areas of the gulf coast of 

 Mississippi, a striking similarity to recent obser- 

 vations in Biscayne Bay, Fla., where many fish of 

 many species now exhibit hemorrhagic lesions be- 

 neath the scales, a condition which was unknown 

 a decade ago (Sindermann 1976). Red sores and 

 associated mortalities have also been described by 

 Rogers (1970, 1972) and Esch et al. (1976) from 

 centrarchid fishes in freshwater reservoirs of the 

 southeastern United States. The disease condition 

 in freshwater seems clearly related to Epistylis 

 infestation, probably abetted by secondary bacte- 

 rial infections, particularly by Aeromonas, al- 

 though there is still some question about which 

 organism is the primary invader. 



It seems likely that generalized disease signs, 

 such as fin rot and red sores (and probably other 

 epidermal lesions such as ulcerations, papillomas, 

 and lymphocystis), may be characteristic of fishes 

 resident in degraded habitats, where environmen- 

 tal stresses of toxic chemicals, low dissolved oxy- 

 gen, and high microbial populations exist. The 

 extent and nature of these external manifesta- 

 tions are probably variable with resistance of the 

 particular species and the extent and nature of 

 environmental degradation. 



Ulcers 



Next to fin erosion, probably the commonest ab- 

 normality reported from fish taken in polluted 

 waters can be identified as "ulceration of bacterial 

 etiology," even though precise bacterial etiology 

 has not been demonstrated in every case. Where 

 bacterial isolations have been made from ulcer- 

 ated tissue. Vibrio anguillarum has been by far 

 the most predominant organism, with pseudo- 

 monads and aeromonads in lesser abundance. 



rainbow trout and testing application factor concept. EPA- 

 R3-73-011C, 80p. 



722 



