206 Conservation Department 



author has collected this parasite from the lakes of Minnesota and 

 Wisconsin and this summer Mr. John W. Titcomb sent some 

 viscera of parasitized black bass from Ontario, Canada. Moore^ 

 lists in addition Michigan, Connecticut, New Jersey, Ohio and 

 New York. The senior author also found the parasite in fish 

 from the ponds of the U. S. Fisheries Station at Neosho, Missouri. 

 Pearse- in addition records the presence of visceral cysts in a 

 number of other species. 



There is great danger of spreading this parasite through the 

 planting of bass from infected hatchery ponds. In such cases the 

 infection may be high and may well serve as a means of establish- 

 ing this harmful helminth in a new locality. Once introduced it 

 stands an excellent chance of surviving due to the number of pos- 

 sible first and second intermediate hosts as well as the relatively 

 large number of definitive hosts. 



Some locality should be sought where the bass are free from this 

 helminth and this should be preserved carefully as a source for 

 breeders. In the case of breeders the fish would be too large to 

 eat each other and so could not bring any plerocercoid larvae 

 back to the intestine where they could reach maturity. Likewise 

 there is danger in following the old policy of securing breeders 

 from the west end of Lake Erie. It was noted that bass taken 

 from the east end of Lake Erie were less heavily parasitized than 

 those from the west end. Thus only 27 per cent of 22 small- 

 mouthed bass sheltered the adult tapeworm compared with 43 per 

 cent of 14 bass taken from the vicinity of Put-in-Bay, Ohio. 

 Even this lower percentage is not low enough, for none of the 

 breeders should be parasitized if we desire to keep the bass in 

 sufficient numbers to retain its place in the heart of the sports- 

 man and tourist. 



Unsolved Problems. — Before any real cures can be effected 

 certain of the remaining problems must be solved. In the first 

 place the maximum period of life in each of the intermediate 

 hosts and the definitive hosts should be determined. This in itself 

 constitutes a very real problem. Secondly, it is important to 

 determine the most successful way of breaking the life cycle and 

 so rendering it possible to control the parasite at least in the 

 hatchery ponds. At present all indications point to the advisability 

 of wiping out the copepods and replacing them with some type 

 of food which cannot carry the larval stages of the tapeworm. 

 That this may be the practical solution of the problem is indicated 

 by the successful production of fish food in various parts of the 

 country. The U. S. Biological Fisheries Station at Fairport, Iowa 

 and Dr. G. C. Embody of Cornell University are working on this 

 problem while the state luitchei-ies at Pratt. Kansas'' and llaeketts- 



'Loc. oil. 



MVarse, A. S. 'I'lic pisrasitcs of lake lislirs. 'I'laiis. Wis. Arad. Sci.. Arts, 

 and U'tters, 21 : Kil-l!) t. 1924. 



'■' Sclinoj2;er}Ter, E. and IVIiima E. Jt'widl. Factors atroctiii'; pond lisli produc- 

 tion. Kansas For.. Fis^h and Game Conim., Bull. No. 0, 14 pp. 1928. 



