Discussion 



PEN and G. hertwigi infected smelt will un- 

 doubtedly be found in other areas, both within and 

 beyond the geogi'aphical range sampled in this 

 study. Management practices involving anadro- 

 mous alewives have inadvertently contributed to 

 the spread of PEN within the State of Maine 

 (Sherburne 1977). Haley ( 1954b) reported similar 

 circumstances for G. hertwigi infected freshwater 

 smelt in New Hampshire. Glugea hertwigi was 

 found in rainbow smelt from Lake Winnisquam, 

 N.H., as well as in other localities where smelt 

 populations were established from the Winnis- 

 quam stock. Smelt that were being transported by 

 the Massachusetts Division of Marine Fisheries 

 from Hingham to Cape Cod, Mass., to initiate new 

 runs during the time of this study had incidences 

 of 99'7f (99/100) PEN and lOV^ (10/100) G. 

 hertwigi . 



Because of the known pathogenicity of G. 

 hertwigi (Haley 1954a, b; Chen and Power 1972; 

 Nepszy et al. 1978), localities with relatively high 

 incidences may warrant further investigation. At 

 the time of the decline of the smelt population in 

 the Great Bay region of New Hampshire in the 

 1950's, 23.3':'f (308/1,3231 of the smelt examined 

 had G. hertwigi (Haley 1954a). Although our 

 samples were considerably smaller, 33.89? (22/65) 

 of the smelt sampled from Kittery and Great Bay 

 were infected with G. hertwigi. The high inci- 

 dences of G. hertwigi (56'7f) at Wyman, South 

 Twin, and Millinocket Lakes were unexpected. 

 However, Chen and Power ( 1972) reported that of 

 1,691 smelt sampled from Lake Erie 62.77f were 

 infected with G. hertwigi. They reported that 

 apart from actual mortality the real significance of 

 G. hertwigi infection lies in its effect on smelt 

 fecundity. In females, parasitic cysts replaced 

 ovarian tissue, causing a serious reduction in the 

 number of maturing eggs. 



There was no apparent relations between G. 

 hertwigi and PEN in the populations sampled in 

 this study. Although smelt at Kingston had high 

 incidences of both PEN and G. hertwigi ( 100/100 

 and 28/100, respectively) other populations with 

 high incidences of PEN did not have high inci- 

 dences of G. hertwigi, i.e., Hingham had 99'100 

 with PEN, 10/100 with G. her-twigi; Addison had 

 100 100 with PEN, 5/100 with G. hertwigi: War- 

 ren had 40 50 with PEN, only 1 58 with G. 

 hertwigi . 



There was no apparent relation between G. 



hertwigi and PEN infections in individuals. Of 135 

 andaromous smelt with G. hertwigi. 71 (52.6"^'?) 

 likewise had PEN. 



Chen and Power (1972) reported seasonal fluc- 

 tuations in G. hertwigi infection from Lakes On- 

 tario and Erie, with the highest incidence during 

 the winter, when smelt were undergoing the most 

 active phase of gonadal maturation. Most of our 

 sampling was confined to winter; therefore, we 

 have no evidence of seasonal fluctuations of PEN 

 and G. hertwigi infections in this study. However, 

 since different areas were sampled at similar 

 times and all fish sampled were adults, the data 

 obtained should afford a representative compari- 

 son between areas. 



This study has determined that PEN and G. 

 hertwigi are widely distributed in rainbow smelt 

 populations along the North Atlantic coast from 

 Massachusetts to the Canadian Maritimes, that 

 the incidence of PEN in each population is high 

 but the intensity of individual infections is low, 

 and that higher incidences of G. hertwigi occur in 

 inland lakes of Maine than in coastal populations. 

 These findings differ from previous studies on the 

 Atlantic cod and Atlantic herring where lower 

 incidences of PEN have been evident but indi- 

 viduals have had nearly every red cell infected 

 (Walker and Sherburne 1977; Sherburne 1973). 



.-Vcknciw kdj;ments 



We thank M. J. Hogan of the Department of 

 Marine Resources and D. C. Harmon of East 

 Boothbay, Maine, for assisting in the field work. 

 Joseph DiCarlo of the Massachusetts Division of 

 Marine Fisheries obtained smelt for us from 

 Hingham and King.ston. We thank Roland Walker 

 of Rensselaer Polytechnic Institute, Jay C. Quast 

 of the Northwest Alaska Fisheries Center Auke 

 Bay Laboratory, NMFS, NOAA, and an anony- 

 mous reviewer who critically reviewed the manu- 

 script and made helpful suggestions to improve 

 clarity of presentation. This study was supported 

 by Public Health Service Grant #5R01HL19163 

 from the National Heart and Lung Institute, Na- 

 tional Institutes of Health and Grant #PCM75- 

 22746 from the National Science Foundation. 



Literature ( ited 



APPY, R. G., M. D, B. BURT. AND T. J. MoRKIS. 



1976. Viral nature of piscine erythrocytic necrosis (PEN) 

 in the blood of Atlantic cod (Gac/i;smf)r/iHH ). J. Fish Res. 

 Boarti Can. 33:1380-1,38.'5. 



508 



