6 EFFECTS OF EXPLOSIVE SOUNDS UPON FISHES. 



cimners {Tautogolahrus adspersus), which began to nibble actively. 

 A motor boat was now backed up under its own power from a dis- 

 tance of about 50 feet till its stern was directly over the baited lines. 

 During the approach of the motor boat the fishes continued to nibble, 

 notwithstanding the increasing noise, till the boat was within 6 feet 

 of the lines, whereupon the fishes ceased nibbling. On running the 

 motor boat away for a short distance, 6 to 8 feet, vigorous nibbling 

 recommenced. It is difficult to say whether the cessation of nibbling, 

 which regularly occurred when the stern of the boat was brought 

 close to the lines, was due to the noise that reached the fishes or to 

 the churning of the water in their neighborhood by the propeller of 

 the boat. However this may be, it is certain that cunners can be 

 driven from bait by a motor boat only when it is very close to them 

 and that they are apparently uninfluenced by the same boat at a 

 distance of 10 feet or so. 



If a cunner can be driven from bait by the disturbance from a 

 motor boat close at hand, other fish maj^ be affected in a like manner, 

 and should these be more sensitive to noises than the cunners, it is 

 possible that they may be influenced when boats are at greater dis- 

 tances than 6 to 8 feet. There is, however, very little conclusive 

 evidence on this point. In August, about the dock at Woods Hole, 

 young bluefish {Pomatomus saltatrix) are not uncommon. They are 

 often angled for with rod and line and afford much sport for the 

 local fishermen. They bite well, even with motor boats making 

 much noise in the harbor and passing the dock at a distance of about 

 a hundred feet. If, however, a motor boat comes close to the dock, 

 they are almost certain to cease biting for a quarter of an hour or 

 so. Observations of this kind are by no means conclusive, but 

 they favor the opinion that some fishes are disturbed by the noises 

 from motor boats, though these disturbances are always very tempo- 

 rary and local. 



The noises produced by motor boats have only a slight and local 

 influence on fishes, not only because the noises that really get into 

 the water are very faint, but probably because they reach the fish in 

 the most favorable way for nonstimulation. Most persons who 

 have experimented with the effects of sound on fishes have been struck 

 with the fact that after a fish has responded once or twice to a given 

 sound, it often ceases to respond to further stimulation for some 

 considerable time, and in experiments of this kind it is usual to allow 

 relatively long intervals of time to elapse between tests in order that 

 the fishes ma}^ return to a receptive state. In the approach of a 

 motor boat the sound that first reaches the fish must be far too faint 

 to call forth any response, and this sound grows so gradually in 

 intensity and with such rapid reiteration that the fish probably 

 acquires the state of nonreaction to sound by the time the stimulus 



