Each experiment, usually included five 3-minute control 

 periods and five 3- minute test periodSo During each period the time 

 spent by the tunny school or schools in the attraction area was meas- 

 ured on an electric clock operated by a push switcho The switch was 

 depressed when the first fish of a school entered the area and was 

 held down until the last fish lefto A fish swimming by itself was ig- 

 nored; often it was a partially=blind or otherwise incapacitated indi- 

 vidual which was unable to keep pace with the otherSo In addition to 

 timing the fish, each "pass" of each fish in either the upstream or 

 downstream direction was recorded on a hand countero ThuSj if 

 three fish swam through the areap the count would be 3o If they en- 

 tered the area, loopedp and left on the same side as they entered, the 

 count would be 60 If they entered the oreao desciibed a connplete 

 circle within the area aJid then left on the opposite side to which they 

 entered, the count would be 9o Time spent in the area was accumu- 

 lated on the clock and the number of passes was accumulated on the 

 covinter. Both were recorded at the end of each 3-nniinute periodo 

 When the tunny population was large (6 to 13 fish), two observers 

 were required on the towerp one of whom clinnbed down and introduced 

 the test material between control and test periods „ a-nd returned when 

 the fish were at the far end of the pond to avoid being seeno When the 

 fish were excited during the early part of a reaction it waa difficult 

 to record all the movementSj even with two observers; in some cases 

 the counts were nninimal estimateSo As in the case of the tank, the 

 difference between control and test periods in average time spent by 

 the fish in the attraction area was used as a measure of attraction 

 and the difference in count was used as a nneasure of the excitement 

 induced by the test substances A typical reaction graph is shown in 

 figure 5o 



In both tank «md pond, in addition to the quantitative 

 mea^flure of reaction discussed above, the observer also indicated 

 the strength of the response in one of several "observational" 

 categories ( - to XXXX). These will be discussed in a later section, 



THE RESPONSE 



A summary of data on 356 experiments which were con- 

 ducted in the tank and pond at intervals over the period July l^ 1952, 

 to May 19, 1953, is given in the appendix a* the end of this reporto 

 The experiments will be referred to by numbeTj eogo Nos„ 168, 170, 

 etCo The results will be discussed in detail in later sections^ For 

 the present, attention will be directed at a description of a typical 

 response in the tank and the pondo 



When aJi attractive substance, such as an extract of tuna 

 flesh, was introduced into the attraction area of the tank, the 



13 



