THE GERMAN CARP IN THE UNITED STATES. 609 



Stiles (1902), of the United States Bureau of Animal Industry. It 

 was learned by Doctor Hutchinson, an inspector of the Bureau in 

 Oregon, that sheep from the lowlands along the Columbia and Wil- 

 lamette rivers, where carp are numerous, are much freer of the fluke 

 disease than those from other sections of the country, and it is sug- 

 gested that the parasites {Fasdola hepatica) which produce the disease 

 may be destroyed by the carp while in a cystic state (cercarise) and 

 attached to the leaves of grass or while they are in their intermediate 

 host, the common fresh-water snail Limnsea. In a letter to the Bureau, 

 dated December 2, 1901, Doctor Hutchinson writes: 



Prof. 0. V. Piper, of the Washington Agricultural College, in conversation with 

 me, mentioned the theory which I find is, as he said, extant in the minds of many 

 farmers along this river, namely, that "leeches" [liver flukes], which were formerly 

 numerous in the livers of cattle and sheep, have to a considerable extent disappeared 

 since the introduction of carp into the waters of this river. 



While, of course, the farmers' idea is that the carp now consume the leech which, 

 according to their view, the cattle formerly swallowed with the water while drink- 

 ing, it is possible that there may be a practical connection between certain peculiar 

 habits of this fish and the noticeable freedom from fascioliasis among the cattle and 

 sheep ranged on the bottoms adjoining streams in which these fish are found, com- 

 pared with animals coming from other sections where carp a r e unknown. About 75 

 per cent of the cattle and sheep coming from the western slope of the Cascades, 

 exclusive of this Columbia River bottom, are infested with Fasciola hepatica; but from 

 this particular portion only about 5 per cent are so infested. 



And in another letter of later date (January 4, 1902) he adds: 



I am able to say that fascioliasis is much less common in animals from the lower 

 Columbia and Willamette slough lands than from any other swampy districts of 

 Oregon or Washington. 



The carp have the more chance to destroy these parasites since the 

 bottom lands are subject to annual overflow, and at such times the fish 

 spread over the meadows and root out and eat much of the grass. 

 Although 1 do not know that any species of Limnsea has been actually 

 identified in the alimentary tracts of carp, there can be no doubt, as 

 Doctor Evermann states in a letter quoted in the above bulletin, that 

 carp do eat them when they are at hand. Doctor Stiles appears to 

 have justification for his final statement that ''the action of the carp 

 in this case appears to be very strongly supported by the facts stated, 

 and it seems that the introduction of carp into fluke districts generally 

 would result in a great decrease of liver-fluke disease." 



The Bureau of Fisheries, as well as some of the state hatcheries, 

 have found that young carp make very good food for black bass, and 

 according to the reports of the Bureau at least 1,000,000 of these small 

 fish must have been used in this way in the years from 1891 to 1896. 

 They have also been used to put into trout ponds to clean out the for- 

 eign matter, to destroy the algae, etc. (Report United States Fish Com- 

 mission for 1900 (1901), p. 57). It is possible that small carp would 



F. C. 1904—39 



