iiio Squid preparations 



Ebcperiments with squid preparations^, either whole or divided 

 into clear and murky portions., yielded no evidence of the presence of 

 attractive substances even when comparatively concentrated prepara- 

 tions were usedo 



As the squid is a normal food of the tunas and as it will expel 

 ink when pursued^ the possibility exists that the combined stimuli of 

 sight and smell might evoke a response whereas either one, acting 

 alone, would not. To test this possibility., Preparation A was made in 

 the following manner o Firesh (thawed) squid C20J4. grams) was extracted 

 without centrifuging, and to this was added the ink of a freshly 

 speared octopus (Polypus mar^moratus ) ^ The material^, when siphoned 

 into the tankj formed a dar-kish cloud which was visible from abovoo 

 Two schooling yellowfin were present, one of which was timedo The 

 results are shown in figure 5o 



In preliminary Tests 1 to ?;, the tuna were attracted by the pre- 

 sence of the observer but settled dovm to normal activity during 

 Tests 8 to 13o Ihile introducing the preparation^ there was an in- 

 crease in cruising speed during Tests 16 and 17o This, howevery can- 

 not be regarded as a reaction to the substance as the behavior was not 

 repeated in a second experimento Moreover, the number of passes 

 across AB remained constant at 5 throughout Tests lU to 21 _« indicat- 

 ing no attractiono 



Although the cloud formed by Preparation A was plainly visible, 

 it was not particularly dark when the preparation became diluted in 

 the tanko As the walls of the tank were also dark, there resmained 

 the possibility that the contrast was not sufficiently sharpo 

 Accordingly, Preparation B was made in a similar manner (3^5 grams 

 of squid) except that India ink was added in such quantity as to pro-= 

 duce a ''pitch" black cloud in the tanko Two yellowfin and one tunny 

 were ^^.^sent, all schooling togethero The results are included in 

 figure 5o 



As indicated in the preliminary tests, for' some unknown reason 

 the fish were restless and cruised around at a relatively high speedo 

 When Preparation B was siphoned into the tank,, the tuna avoided the 

 black cloudg remaining close to the south wall (figo 2), and not 

 crossing the line^ ACo The doud diffused across the tank and gradual- 

 ly drifted towards the south wallo As it apprca':Aedj the yellowfin 

 became more snd more excited, and finally darted through it., there- 

 after remaining in the up=stream portion of the tank until practically 

 all of the cloud had dispersed through the overflow„ Ihe tunny showed 

 an entirely different behavior., appearing to be undisturbed by the 

 presence of the black clcudo It cruised into and cut of the cloudj, 

 maintaining an approximately constant speedo 



16 



'y 



