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 (/asciola hepatica) which produce the disease 
may be destroyed by the carp while in a cystic state (cercarie) and 
attached to the leaves of grass or while they are in their intermediate 
host, the common fresh-water snail Zimneza. Ina letter to the Bureau, 
dated December 2, 1901, Doctor Hutchinson writes: 
Prof. C. 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 toa 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 are 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 I do not know that any species of Zimnza 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 1894 to 1896. 
They have also been used to put into trout ponds to clean out the for- 
eign matter, to destroy the algw, etc. (Report United States Fish Com- 
mission for 1900 (1901), p. 57). It is possible that small carp would 
F. C. 1904—39 
