710 
FOREST AND STREAM. 
[Nov. n, 1911. 
Effects of Explosive Sounds on Fishes 
By G. H. PARKER, S.D., Professor of Zoology, Harvard University 
T HAT sounds affect many fishes has long 
been recognized by fishermen and natu¬ 
ralists. No less an authority than Izaak 
Walton declared that it should be a rule with 
him to make as little noise as possible when he 
was fishing, lest he be heard and catch no fish. 
Nevertheless, it has been only within the last 
few years that the sense organs concerned with 
the reception of sound in fishes have been defi¬ 
nitely identified. 
Using the term sound to include any vibra¬ 
tions of the water, from such slight movements 
as result from waves and currents to the vibra¬ 
tions that emanate from the impact of solid 
bodies under water or from the more violent dis¬ 
charge of explosives, it may be said that sounds 
affect fishes through three sets of sense organs— 
the skin, the lateral line organs and the ears. 
Within recent years it has been demonstrated 
that a fish can feel sounds through its skin in 
much the same way that a human being can feel 
the vibrations of a musical instrument when his 
hand is in contact with it. It has also been 
demonstrated that certain fishes sense relatively 
low vibrations, such as trembling movements of 
the water, by means of the lateral line organs. 
And furthermore, though this point has been 
disputed, it seems clear to the writer through 
work carried out under the auspices of the Bureau 
of Fisheries that the internal ears of fishes 
are not only organs for the adjustment of bodily 
motions and equilibrium, but a'so organs of 
hearing. 
If, then, fishes are sensitive through so many 
channels to sounds, the question naturally arises 
as to the effect of the introduction of motor 
boats and other sound-produc’ng mechanisms on 
the fishes of our shores. 
To the human ear under ordinary circum¬ 
stances most motor boats either with or with¬ 
out mufflers are noisy appliances, generating 
sounds that are carried a long distance through 
the air. But in the water these sounds are very 
much less penetrating. To test this, a seven 
horsepower motor boat with an exceptionally 
loud sound was run in open water and an ob¬ 
server p'unged under the surface as the boat 
passed. When within ten or twelve feet of the 
boat, whose escape pipe was in the air, the ex¬ 
plosions of the gas could be faintly heard, though 
they were disagreeably loud to the observer when 
in the air. With the escape pipe under water 
and at the same distance as before the no : se of 
the explosions could scarcely be detected at al> 
under water. Thus both methods of running 
the boat delivered into the water surprisingly 
little sound as compared with what escaped into 
the air, and of the two conditions the muffled 
boat yielded to the water much less sound than 
the unmuffled boat. 
In testing the effect of the motor boat noises 
on fishes, a number of kinds of fish known to 
be sensitive to sounds, such as killifish, young 
scup and young kingfish were placed in a large 
wooden cage, four feet square by about two feet 
deep, whose walls were of strong netting. This 
*From Bureau of Fisheries Document No. 752. 
cage was fastened in quiet water at the end of 
a float and a motor boat of three and one-half 
horsepower, and with a penetrating noise was 
at a distance of some 400 feet from the cage and 
run at full speed past it. 
An observer was stationed on the float to note 
any response made by the fish. Tests were made 
with the escape pipe out of water, and with it 
under water, but in neither instance was there 
any apparent effect upon the fishes. Most of 
these fishes, and especially the kil.ifish, go down 
into deeper water when only slightly disturbed, 
but in these trials they remained playing about 
on the surface of the water, while the boat 
passed and' were in no observable way disturbed 
until the swash from the boat struck the cage, 
whereupon they generally dove to the deeper 
part of the receptacle. 
Another test of a like kind was carried out on 
mackerel. About thirty of these fish that had 
been for one or two days in a large pocket at 
the end of a pound net about a quarter of a 
mile from shore were gathered together by hav¬ 
ing the pocket pursed up into a space about 
twenty-five feet square and ten feet deep. In this 
space they swam slowly about in a circle near 
the top of the water. 
When an observer stationed in a boat at the 
edge of the pocket rose in the boat, the fish very 
usually went to the bottom of their inclosure, to 
return to the surface after the observer had 
taken his seat again. While the observer was 
sitting and watching the fish, a second person 
ran a motor boat over a circular course about 
half a mile in circumference, the course passing 
close to the pocket at one point. As the motor 
boat passed the pocket, the fish were closely 
scrutinized by the observer. In no instance, 
either with the escape pipe of the motor boat 
above water or under water, did the mackerel 
sink into the deeper part of the pocket nor did 
they show in any other observable way that they 
were disturbed by the noise from the boat. Seven 
of them were then isolated in the cage previously 
mentioned am 1 tested under close inspection by 
running the motor boat past the cage, but again 
the mackerel gave no evidence of being disturbed 
by the noise. 
Although these tests seem to be quite conclu¬ 
sive in showing that the faint noises produced 
in the water by a motor boat have no marked 
effect on the ordinary activities of certain fishes, 
it is not impossible that the same noises may 
interfere with other activities of these fishes, 
such as feeding, pairing, egg laying, etc. The 
only tests in this direction that were carried out 
had to do with feeding. Hungry killifish, scup 
and kingfish were placed in the cage previously 
used, and the cage was fastened to a float so 
that a motor boat could pass close to it. When 
the fish were feeding vigorously, the motor boat 
was run by the cage several times, but in no 
case did the fish give up feeding in consequence 
of the noise. 
Two baited fish lines were lowered from the 
edge of a wharf until the bait was about six 
feet under water. In a short time the two baits 
were surrounded by cunners, which began to nib¬ 
ble actively. A motor boat was now backed up 
under its own power from a distance of about 
fifty feet till its stern was directly over the 
baited lines. During the approach of the motor 
boat the fishes continued to nibble, notwithstand¬ 
ing the increasing noise, till the boat was within 
six feet of the lines, whereupon the fishes ceased 
nibbling. On running the motor boat away for 
a short distance, six to eight feet, vigorous nib¬ 
bling recommenced. It is difficult to say whether 
the cessation of nibbling, which regularly oc¬ 
curred 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 ten feet or so. 
If a cunner can be driven from bait by the dis¬ 
turbance from a motor boat close at hand, other 
fish may be affected in a like manner, and should 
these be more sensitive to noises than the cun¬ 
ners, it is possible that they may be influenced 
when boats are at greater distances than six to 
eight feet. There is, however, very little con¬ 
clusive evidence on this point. In August, about 
the dock at Woods Hole, young bluefish 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 pass¬ 
ing 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 favor the opinion that some fishes are 
disturbed by the noises from motor boats, though 
these disturbances are always very temporary 
and local. 
The noises produced by motor boats have only 
a slight and local influence on fishes, not only be¬ 
cause the noises that really get into the water 
are very faint, but probably because they reach 
the fish in the most favorable way for nonstimu¬ 
lation. Most persons who have experimented 
with the effects of sound on fishes have been 
struck with the fact that after a fish has re¬ 
sponded 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 may 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 re¬ 
iteration that the fish probably acquires the state 
of nonreaction to sound by the time the stimulus 
has grown to such an intensity as would have 
been effective had a single shock been delivered 
at once to the fish. The gradual approach of the 
boat then does away with the element of con¬ 
trast between silence and loud noise, and the re¬ 
sult is just the reverse of that of summation, 
so often seen in the application of minimal 
stimuli to sense organs; the fish fails to respond. 
As long ago as 1782, Hunter demonstrated that 
fishes were responsive to the discharge of a fowl¬ 
ing piece. In his account of the internal ears 
of fishes he states that “in the year 1762, when 
I was in Portugal, I observed in a nobleman’s 
