of building up a conditioned reflex to sound, and that some species of 

 fish were affected more than others,, 



The point to be made is that experimentation with sound need not 

 necessarily involve complex equipment. Experiments such as those of 

 Moorhouse could be duplicated by anyone, A simple device such as a 

 pneumatic drill operating in a submerged tank might prove effective as 

 a fish "scare". It would then be the province of the electronics 

 experts to measure the sound and reproduce it in a controlled manner 

 for the purpose of guilding small fish. 



Although it has been mentioned in the literature that fish tend 

 to be attracted to low frequency sound waves, such statements apparently 

 are not based on more than single observations. The majority of the 

 research work in relation to sound and fish has been concerned with the 

 ability of fish to be conditioned to respond to a sound stimulus. Such 

 experiments have shown that most fish condition readily and serve as evi- 

 dence that most fish are capable of sound perception. There is, however, 

 little if any indication that fish are consistently attracted or 

 repelled by sound waves of any frequency or amplitude. 



The evidence that the four pieces of professional sound equipment 

 described in this report failed to produce a marked forcing or guiding 

 response in young salmonoids does not detract from the desirability of 

 presenting the methods and results of the experiments, nor should 

 investigators consider that the frequencies tested have been exhaustively 

 covered by these tests. Sound wave qualities and the kinds of trans- 

 ducers used to force this energy into the water are so diverse that the 

 present work must be considered as only exploratory. 



EQUIPMENT AND METHODS 



Rainbow trout from h to 9 inches in length (Figure 1) and l/2 

 inch brown trout were used in most of the tests. The fish were all 

 normal healthy hatchery trout, taken for the most part, from natural 

 rac eways „ 



The physical equipment set up to measure the reaction of fish to 

 sound by actual count is shoim in Figures 2, 3, h, and 5, Tliis con- 

 sisted simply of a 1/2 inch mesh wire trough, 100 feet long and 3 feet 

 wide by 3 feet deep with just enough wood framing for support of the 

 wire, plank gangway and the nine gates separating the trough into ten 

 sections ten feet long each. No unnecessary wood was used under water 

 because of possible reflection of sound waves from structural members. 

 The bottom seams of the wire trough were joined by hog rings at 2-inch 

 intervals (Figure 2) , so that the entire trough was literally suspended 

 from the 1 x U longitudinal members, with the wire bottom a foot above 

 the mud bottom of the pond. The nine gates separating the trough into 

 ten sections were so rigged that all could be raised or dropped simul- 



