NOTES 



EFFECTS OF LONG-TERM MERCURY 



EXPOSURE ON HEMATOLOGY OF 

 STRIPED BASS, MORONE SAXATILIS 



The striped bass, Morone saxatilis, is found 

 along the shore of the heavily populated Atlantic 

 coast of North America; hence, it is subjected to 

 considerable domestic and industrial pollution. 

 Even higher pollutant concentrations may be 

 encountered when the fish migrate into rivers to 

 spawn. Because of the availability of the species, 

 its value to both commercial and sport fisheries, 

 and its normal habitat in many areas where pol- 

 lution is a problem, the striped bass may be a 

 particularly appropriate indicator species for 

 pollution studies. In spite of these factors, in- 

 formation about sublethal effects of metal on 

 striped bass is limited; even the response of the 

 species to mercury, perhaps the most widely 

 studied heavy metal, has received little attention 

 in the literature. 



That fish accumulate mercury from water has 

 been demonstrated both in the laboratory and in 

 the wild. Pentreath (1976). in a study of accumu- 

 lation, distribution, and retention of mercury, 

 found a gradual uptake and slow loss of 

 :03 mercury in the plaice, Pleuronectes platessa, 

 during laboratory exposures up to 90 d. Olson et 

 al. (1973) showed that the rainbow trout, Salmo 

 gairdneri, accumulates mercury through the 

 gills. Our laboratory demonstrated uptake of 

 mercury into the winter flounder, Pseudopleuro- 

 nectes americanus, during a 60-d laboratory 

 exposure (Calabrese et al. 1975). Mercury 

 analyses on fish taken from their natural envi- 

 ronment corroborate the laboratory findings: An 

 increasing mercury concentration correlated 

 with increasing weight has been demonstrated 

 in the pike, Esox lucius; the bluefish, Pomatomus 

 saltatrix; the blue hake, Antimora rostrata; and 

 the striped bass(Johnelsetal. 1967; Alexander et 

 al. 1973; Cross et al. 1973). 



The sensitivity of striped bass to pollution in 

 general has been reported by a number of inves- 

 tigators. Raney (1952) noted that, although the 

 striped bass had formerly used as spawning 

 areas most of the large rivers along the Atlantic 

 coast of the United States, the species had 

 virtually disappeared from many of these areas, 

 notably the Delaware, Connecticut, and Roanoke 



Rivers; he attributed its disappearance to gross 

 pollution. Chittenden (1971) also attributed the 

 lack of striped bass in the Delaware River to 

 gross pollution and suggested that a major 

 limiting factor was the river's very low oxygen 

 content. An earlier study in our laboratory 

 demonstrated sublethal responses of the striped 

 bass to mercury. Juvenile striped bass were ex- 

 posed to 5 and 10 parts per billion (ppb) mercury 

 for periods ranging from 30 to 120 d. Measure- 

 ments of gill-tissue oxygen consumption showed 

 changes whose magnitude and direction varied 

 with length of exposure (Dawson et al. 1977). 



The present study was undertaken to deter- 

 mine the nature and extent of physiological dis- 

 turbance to striped bass caused by mercury 

 exposure using a variety of hematological tests. 

 Variables related to the oxygen-carrying 

 capacity of the blood, such as hemoglobin and 

 hematocrit, were considered important because 

 of earlier indications that mercury exposure 

 affects respiration (Dawson et al. 1977), because 

 of the suggestion that low oxygen levels 

 eliminate striped bass from certain polluted 

 environments (Chittenden 1971), and because of 

 evidence that mercury affects these measure- 

 ments in other fish (Calabrese et al. 1975; 

 Dawson 1979). In addition, because my earlier 

 work indicated that mercury disrupts osmo- and 

 ion-regulation in winter flounder(Dawson 1979), 

 I included these aspects of plasma chemistry in 

 the present study. 



Methods 



Exposure 



Striped bass were obtained from the Edenton 

 National Fish Hatchery, U.S. Fish and Wildlife 

 Service, Edenton, N.C., where they had been 

 reared in freshwater. Upon arrival at the North- 

 east Fisheries Center Milford Laboratory, they 

 were placed directly into flowing Milford 

 Harbor seawater and allowed to acclimate for 2 

 wk prior to exposure. Throughout the acclima- 

 tion and the exposure period the fish were fed 

 Purina Trout Chow 1 ad libitum, daily. The fish 



1 Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



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



389 



