8 EFFECi'S OF EXPLOSIVE SOUNDS UPON FISHES. 



a foot or HO of water it resembled the pop of a soda-water bottle 

 both in quality and in intensity. This great reduction in intensity 

 of the sound, as in the case of the motor-boat sounds, results from 

 the reflection of most of the sound from the surface of the water, 

 and hence its failure to enter the water. Yet the little that did enter 

 the water sufficed to stimulate the fishes. 



Fundulus is known to be quite sensitive to sound, but the fact 

 that it lives under water renders it relatively inaccessible to sounds, 

 since most sounds originate in the air. This explains why Fundulus 

 and most other fishes fail to respond to the human voice. It is not 

 that the hiniian voice in itself is not strong enough to stimulate a 

 fish, but rather that so little sound from it enters the water that 

 stimulation is impossible. The surface between water and air is for 

 fishes an effective screen through which very little sound can pass. 



With the view of ascertaining something of the effectiveness of a 

 gun report as a stimulus for Fundulus^ trials were made by firing 

 the gun at various distances from the cage of fish. Fundulus in- 

 variably responded to the discharge of the gun at 100 feet from the 

 cage; they usually responded at 200 feet; but they never responded 

 at 500 feet. From these observations it is evident that the effect of 

 the report of a gun is distinctly local and in this respect it re- 

 sembles the motor-boat noises. 



It would be a matter of great interest to ascertain what influence 

 the firing of heavy guns has on fishes, but thus far no good oppor- 

 tunity for prosecuting such investigations has been found. Through 

 the courtesy of the commanding officer of the United States revenue 

 cutter Gresham it was possible to study the effect of the explosion 

 of a saluting charge of 2 pounds of powder from a 6-pound howitzer. 

 In these tests a considerable number of Fundulus were retained in a 

 cage and the tests made at varying distances from the gun. At 

 2,000 feet no response was given to the report, and the same was 

 true at 1,000 feet. Within 30 feet of the gun the conditions for 

 accurate observation, because of the heavy detonation, were very 

 unfavorable, but the response at this position was at most only 

 momentary and certainly not more striking than the reaction to the 

 report from a fowling piece. 



From these observations it seems quite clear that single, loud 

 noises generated in the air enter water to a small extent, but in 

 sufficient volume to disturb momentarily fishes that are in the im- 

 mediate vicinity. But even this limited disturbance does not seem 

 to be produced by the ordinary motor boat which, partly because of 

 the faintness of its sound under water and partly because of the 

 gradual increase and decrease of the sound in intensity as the boat 

 approaches and recedes, is relatively inert so far as many fish are 

 concerned. 



