INTERNAL PARASITES OF THE SEBAGO SALMON. 



II75 



introduced at the same time with the primary host and its parasites to which 

 they are related, or, finally, there must be present in the fresh water other animals 

 which can serve successfully as intermediate hosts. The interrelation is thus very 

 complicated and the chance of achieving it so small that in most cases marine 

 forms do not bring the majority of their parasites with them in the transfer to 

 fresh-water existence. In other words, limnetic animals are less heavily para- 

 sitized than marine. For this reason the examination of so recent a migrant 

 into fresh water as the Sebago salmon is of great biological interest. 



At Lake Sebago only 7 specimens of the Sebago salmon were obtained and 

 examined. These weighed, respectively, 2, 2, 2, 3, 5 >^, 8, and 16 pounds. While 

 the number examined was from one standpoint small, yet in view of the scarcity 

 of the species in the lake it was fortunately large. The series was also representa- 

 tive of different ages, ranging probably over several years in growth. It seems 

 likely that if marked variations in food materials were found such a range of 

 specimens would indicate the fact through differences in parasitic infestation. 

 Yet there was a striking uniformity in the records in the series. Furthermore, 

 the fish were all examined very soon after capture, and thus any post-mortem 

 wanderings, which certainly do influence the location of parasites collected 

 from market fish, were largely avoided. No doubt there are rare parasites of 

 this species which are not represented in this collection, but, all things being con- 

 sidered, it may be asserted with some confidence that the records give a true 

 picture of the number and location of the parasites infesting them. 



The parasites found are recorded in the following table : 



Record of Parasites from Salmo sebago. 



[x— many, xx^ very many. §=more than in fish no. 14— not counted.] 



o Also in swimming bladder (?). See text. & Viscera a mass of adhesions; parasites difficult to pick out. 



