(2) if the fish were attracted by some quality or 

 quantity of sound, the fish would tend to pro- 

 ceed to the end of the tank nearest the sound 

 source; (3) if the fish were frightened by the 

 sound, they would travel away from the sound 

 source. It was also assumed that other stimuli 

 had no effect on the movement of the fish. As 

 explained previously, precautions were taken 

 so far as possible against extraneous stimuli 

 such as light, movement of persons, and other 

 disturbing factors . 



LABORATORY PROCEDURE 



The final procedure for testing was the re- 

 sult of numerous exploratory trials. For 

 systematic testing, the method adopted was to 

 place 25 fish in the first compartment of the 

 tank, with the separators in the "down" position. 

 When the fish had settled down and had become 

 adjusted to their surroundings, the separators 

 were raised. While the separators were in the 

 "up" position, the fish were free to move any 

 place within the tank. After a 10 -second per- 

 iod, the separators, were lowered, thus trapping 

 the fish in the various compartments. The dis- 

 tribution of the fish within the tank was then 

 recorded. 



Each sound test was accompanied by a 

 control, the only difference betweenctest and 

 control conditions being the introduction of 

 sound during the 10 -second period when the 

 separators were in the "up" position. Controls 

 were without the introduction of sound. For 

 each condition of sound being tested, there were 

 five controls and five sound tests . In conducting 

 a test, first a control was run with all the fish in 

 compartment No. 1, which was adjacent to the 

 transducer. Immediately following the control, 

 a sound test was run under exactly the same 

 conditions except for the introduction of sound 

 during the 10-second period. This procedure 

 was repeated in compartments Nos. 1 to 5, thus 

 constituting a test series of the particular noise 

 condition as a repelling force. Some test series 

 were duplicated for ease in statistical analysis. 



This method of testing was chosen 

 after a considerable amount of exploratory 

 testing. The Service's statistical service 

 unit in Seattle advised that this method be 

 used, on the basis of the following reason- 

 ing: If sound proved to be effective to any 

 measurable degree as a repelling force, it 

 is logical to assume that it would be demon- 

 strated more easily when the fish are 

 started in the compartment closest to the 

 sound source. Likewise, if sound should 

 prove effective as an attracting foirce, it 

 should be demonstrated most readily when 

 the fish are started in compartment No. 5, 

 the most distant from the sound source. 



OPEN -WATER METHODS AND 

 EQUIPMENT 



Because frequencies below about 

 500 c.p. s. were not giving a reliable pat- 

 tern of sound in the tank, it was concluded 

 that low -frequency testing should be done 

 in a large body of water. Open -water 

 testing would eliminate such problems as 

 the limited dimensions of a tank and would 

 permit testing with relatively few obstruc- 

 tions to the soundwaves. Consultations 

 with underwater -sound engineers verified 

 this conclusion, and plans were made for 

 the construction of a floating laboratory for 

 use on Lake Washington. Permission was 

 granted to the Fish and Wildlife Service by 

 the Navy Department to moor the floating 

 laboratory at the Sand Point Naval Air Sta- 

 tion, Seattle, Washington. 



The floating laboratory was a raft, 

 16 by 32 feet, constructed of four large 

 cedar logs with 30-inch -minimum butts 

 held together by 6- by 8 -inch stringers 

 placed 18 inches on center. The decking 

 was of 2- by 6 -inch fir . As shown in figure 5; 

 there was a rectangular opening in the deck 

 just forward of the cabin. The opening was 

 between the two innermost float logs and 

 allowed easy access to the underwater pens 



