II56 



BULLETIN OF THE BUREAU OF FISHERIES. 



Without tracing in detail the further progress- of the record, it mav 

 be said that at the present date the hst includes 47 species, which are 

 enumerated later in this paper. It is of importance for a consideration of the 

 distribution of the salmon parasites, the especial object of this paper, to review 

 the later studies in this field in their geographic arrangement in order to com- 

 pare clearly the parasites found in one area with those which are present in 

 another. The salmon which have been most intensively studied are those of 

 the Rhine. 



Our knowledge of these forms is due largely to a series of papers by the 

 distinguished Swiss helminthologist, Fr. 7,schokke, of Basel, which cover the 

 work of many years. The first record of Zschokke (1889) included examina- 

 tions of 45 fish, of which 42 were found infected with parasites. All the fish 

 were caught in the Rhine in November, December, and January, and the 

 following parasitic species were listed : 



Not a single parasite lay in the alimentary canal below the pyloric coeca. 

 Monticelli notes that most sharks lose their parasites after a long stay in an 

 aquarium, and Zschokke has observed that marine fish otherwise heavily 

 infested lose their intestinal parasites very rapidly when subjected to fasting 

 in captivity. The Rhine salmon behaves with regard to parasites just like 

 a fasting sea fish. Its parasitic fauna manifests an almost purely marine 

 aspect. Fresh-water elements are scanty and insignificant. Clearly, then, the 

 Rhine salmon takes little or no food during its fresh-water migration. Data 

 on individual species close the paper. 



The parasitic fauna of the Atlantic salmon was discussed in extended 

 fashion later by Zschokke (1891) on the basis of his own previous studies and 

 those of earlier authors. In all he had examined the viscera of 129 fish caught 

 in the Rhine. The alimentary canal contained in all cases the thick yellowish 

 or yellow-brown mucus, but never any recognizable remnants of food mate- 

 rials, although once plant fibers and undigested remains of a Gammariis pulex 

 were found. As in similar previously reported cases, so here also the occur- 

 rence of these fragments should be regarded as purely accidental. 



