COPEPOD PARASITES OF FRESH-WATER FISHES AND THEIR 

 ECONOMIC RELATIONS TO MUSSEL GLOCHIDIA. 



By CHARLES BRANCH WILSON, Ph. D. 

 State Normal School, Westfield, Massachusetts. 



Contribution from the United States Fisheries Biological Station, Fairport, Iowa. 



INTRODUCTION. 



Under an appointment by the Commissioner of Fisheries, during the summer of 

 1914, at the United States Fisheries biological station at Fairport, Iowa, an extended 

 examination was made of the parasitic copepods which infest our fresh-water fishes in 

 the Mississippi River and its tributaries and of the mussel glochidia which are also 

 parasitic upon fish during their term of metamorphosis. Several of the early American 

 naturalists became interested in the copepods found upon fresh-water fish, and many 

 new species were described. This was especially true of Le Sueur and Dana, and singu- 

 larly enough the Danish investigator, Kr0yer, also obtained a number of American species 

 from fish sent to the Copenhagen Museum. But in every instance the species described 

 were isolated, they were sometimes founded upon single specimens, and many of them 

 have never been seen since their original discovery. 



Prof. S. I. Smith published in the Report of the United States Commissioner of Fish 

 and Fisheries for 1872-73 aUst of the crustacean parasites of the fresh-water fishes of 

 the United States (p. 661-665). This list included two arguHds, one caUgid, one ergas- 

 ilid, six lemaeopods, three of which were new to science, and two lemseans, 12 species 

 in all. With true scientific foresight, Prof. Smith stated that the few species he enumer- 

 ated were "doubtless only a small fraction of those which really prey upon our common 

 fishes," and that his principal object was to "call attention to the subject and furnish 

 a basis for future investigation" (p. 661). But his suggestion did not meet with the 

 response it deserved and beyond the investigations of Smith himself, Packard, Kelli- 

 cott, Wright, Fasten, and a few others, all widely scattered, no attempt has been made 

 to increase the list up to the time of the present investigation. 



About 1895 Mr. R. R. Gurley, at that time in the employ of the United States 

 Bureau of Fisheries, gathered together all the available data with reference to the 

 copepods parasitic upon fresh-water fishes, translating the descriptions given by Kr0yer 

 and other foreign investigators and identifying both hosts and parasites amongst the 

 material in possession of the Bureau. He made no attempt to establish new species, 

 but only to bring together all that had been previously described, and he accumulated 

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