592 REPORT OF THE COMMISSIONER OF FISHERIES. 



also cuts off the .young- shoots when building its nest, and at such 

 times these may be found floating on the surface of the water. 



In conclusion, as to the relation of carp to aquatic vegetation, the 

 evidence seems to be pretty strong that in general they are very 

 destructive, and are probably, in large part at least, responsible for 

 the great reduction of wild celery and wild rice that has been noted in 

 many of our inland marshes in the last few years. This, in turn, has 

 deprived certain ducks, especially the canvasback and redhead, of an 

 important food supply, and has undoubtedly influenced their abun- 

 dance to some extent in the localities in question. Whether the great 

 reduction in their actual numbers can be laid to this cause is a very 

 different question; and when we observe that the same complaint is 

 being made of nearly all game birds and mammals not rigorously pro- 

 tected by law, it makes us look for an influence at work more general 

 than the introduction of carp into our waters. Such an influence is to 

 be found in the hunters themselves, and must be reckoned with in the 

 case of the ducks as well as elsewhere. Whether it is more or less potent 

 than the reduction of one of their sources of food is a question which 

 remains to be settled. It is possible, too, that with the development 

 of the country, and especially the opening up of extensive areas by 

 irrigation, the ducks, instead of being actually so decreased in num- 

 bers as would at first seem to be the case, have scattered to new feed- 

 ing grounds. A portion of the following quotation from the paper by 

 Smith (1896, p. 399), mentioned above, refers to this possibility, while 

 it also sums up in a concise manner the other aspects of the question: 



In attributing to the carp the scarcity of canvasback and other ducks in a given 

 region, there should be proof that the carp does and other fish do not eat and uproot 

 large quantities of VaUisneria; and the influence of market hunters and indiscrimi- 

 nate killing by sportsmen must not be overlooked. The scarcity of canvasback ducks 

 in most streams probably antedates the advent of the carp in noteworthy numbers, 

 and, as in the Potomac, was coincident with spring shooting and with the activity of 

 pot-hunters using swivel guns. Mr. John P. Babcock, chief deputy of the California 

 fish commission, states that he thinks ducks in that State have changed their feed- 

 ing grounds; miles of land in the San Joaquin Valley are now covered with ditches 

 and miles of alfalfa now grow where a few years ago there was a desert; and the 

 main market supply of ducks comes from that region instead of the Suisun Marshes. 

 He thinks, however, that the carp have proved very objectionable in this region. 



In consideration of all the evidence set forth above, although we are 

 obviously unprepared to say to what extent, we seem forced to conclude 

 that carp are, in some measure, detrimental to certain species of ducks. 



ROILINESS OF WATER INHABITED BY CARP. 



The extent to which carp stir up the bottom mud and make the water 

 roily has been mentioned in speaking of its habits, and especially its 

 manner of feeding. As a general thing this is one of the surest indica- 

 tions of the presence of these fish in waters that would otherwise be 



