THE INTERRELATION OF WATER QUALITY, GILL PARASITES, AND 

 GILL PATHOLOGY OF SOME FISHES FROM SOUTH BISCAYNE BAY, 



FLORIDA 



Renate H. Skinner 1 



ABSTRACT 



This study investigated monogenetic trematode infestation of the gills and gill pathology of yellow- 

 fin mojarra, Gerres cinereus (Gerreidae); gray snapper, Lutjanus griseus (Lutjanidae); and timucu 

 (needlefish), Strongylura timucu (Belonidae) in relation to water quality in south Biscayne Bay, 

 Florida. Two habitats of the three species in the bay, one in the southeast and the other in the south- 

 west, differed in water quality whereas physical and environmental parameters were similar. The 

 water in southwest Biscayne Bay contained.high amounts of ammonia, trace metals, and pesticides 

 which were not present in the southeast bay. The gills of hosts from the habitat with inferior water 

 quality were heavily infested with the Monogenea (Platyhelminthes) Neodiplectanwm wenningeri 

 (on G. cinereus), Ancyrocephalus sp. (on L. griseus), and Ancyrocephalus parvus (on S. timucu) and 

 suffered from excessive mucus secretion, epithelial hyperplasia, fusion of gill lamellae, clubbing 

 and fusion of filaments, and aneurisms. Only light infestations and little or no abnormal tissue 

 changes were noted in fish from the area of good water quality. The findings led to the conclusion 

 that the pollutants in the water acted as an irritant, stressing the fisji, and producing physical and 

 physiological changes which reduced resistance to infestation by Monogenea. 



Manmade pollution of coastal waters of south- 

 east Florida has reached a critical level in the 

 most populated areas, causing substantial envi- 

 ronmental degradation (Carter 1974) and the 

 loss of valuable fishing grounds, and making 

 some areas unsuitable for recreation. In recent 

 years, the pollution of Biscayne Bay, Fla. (Fig. 1) 

 has become a major issue. The shore of north Bis- 

 cayne Bay is bordered by Miami and Miami 

 Beach, and lined by bulkheads. It receives a 

 large amount of runoff water from the metropol- 

 itan areas (Waite 1976). Although the south- 

 western part of the bay still retains much of its 

 natural shoreline and mangrove forests, it is 

 broken by drainage canals intended to lower the 

 water level in neighboring agricultural and ur- 

 ban areas. These canals therefore carry agricul- 

 tural, industrial, and urban wastes into that part 

 of the bay (Waite 1976). The southeastern shore- 

 line of Biscayne Bay is formed by a chain of 

 islands which is part of Biscayne National Park 

 with no major direct sources of water pollution. 

 The purpose of this study was to investigate if 

 differences existed in the ectoparasite fauna and 

 possible gill pathology in the same three species 

 of fish living in southwest Biscayne Bay in the 



'3834 El Prado Boulevard, Miami, FL 33133. 



Manuscript accepted November 1981. 

 FISHERY BULLETIN: VOL. 80. NO. 2. 1982. 



entrances of three drainage canals on one hand 

 and the relatively clean waters of the southeast 

 bay in the National Park on the other. The effect 

 of water quality on the incidence and intensity of 

 infestation by ectoparasites was investigated 

 along with the frequency and kind of abnormal 

 tissue changes of the gills. Included were those 

 ectoparasites that came close to 100% incidence 

 on their hosts and had a direct life cycle. Three 

 species of Monogenea of the suborder Monopis- 

 thocotylea fell into this category. 



Monogenea (Platyhelminthes) of the gills are 

 common in fish. Since parasites affect the health 

 of fish, they can be the cause of or a contributing 

 factor to host mortality and epizootics (Iversen et 

 al. 1971). Disease and mass mortality in aquacul- 

 ture, often occurring under crowded conditions, 

 are known to have been caused by the genera 

 Gyrodactylus, Dactylogyrus, and Tetraonchus 

 (Wobeser et al. 1976). Since exchange of gases in 

 the gills takes place through a single thin epithe- 

 lial layer separating the blood from the external 

 environment (Anderson and Mitchum 1974), 

 parasites may cause extensive damage to host 

 gill tissue. 



Although many adverse circumstances weak- 

 en fish and make them more susceptible to dis- 

 eases, presently available literature is mainly 

 concerned with bacterial diseases (Pippy and 



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