INTERNAL PARASITES OF THE SEBAGO SALMON. 



By HENRY B. WARD, Ph. D., 



Projessor of Zoology, University of Illinois. 



In connection with other investigations of the United States Bureau of 

 Fisheries in Alaska in 1906, I had the privilege of spending two months in study 

 of the parasites of the Pacific salmon. The following year, for comparison of 

 the interesting results of this work with similar studies of Atlantic salmon, I 

 was designated to join a party engaged in a biological survey of Lake Sebago, 

 Maine. During six weeks in this region I examined for parasites a number of 

 the Sebago salmon and secured a series of parasites from other fish in the lake 

 and adjacent waters. 



The large amount of valuable material obtained on these two trips has 

 engaged my entire attention during the interval since it was secured, and even 

 yet some questions have not been satisfactorily answered. It forms a most 

 interesting contribution to the parasitic fauna of these important fishes and at 

 the same time throws some light on the general relations between an animal 

 and its parasites, which I hope may be of interest to the scientist and of value 

 to the practical fish culturist. This report falls naturally into three parts — 

 first, a historical summary, which concerns chiefly the European or Atlantic 

 salmon, since this species is the only one that has been studied previous to 

 the present date; second, a report on the findings in the case of the Sebago 

 salmon, which is very closely related to the European species, together with a 

 discussion of the conclusions which may be drawn from these data; and third, 

 a similar report on the Pacific salmon, which is less closely related and rather 

 widely removed geographically from the other two forms. In the present paper 

 are included only the first and second sections of the entire report. 



HISTORICAL SURVEY. 

 PARASITES OF ATLANTIC SALMON. 



Rudolphi says that in 1726 Frisch observed a salmon parasite, later known 

 as Bothriocephalus solidus, and in 1735 published some record of its occurrence 

 in a paper entitled " De taniis in pisiculo aculeato, qui in Marchia Brandenburgia 

 vocatur 'Stecherling.' " This is the first account of a salmon parasite to which 

 I have found any reference, and I have been unable to ascertain more precisely 

 the data in this case or to verify the reference. 



"53 



