inlet after about 30 seconds > They became greatly excited and often 

 bit into the rubber tube. Some 10 minutes after siphoning started^ 

 the excitement subsided and some 5 minutes later they resumed their 

 cruisingc The yellovrfin were markedly excited and were definitely 

 attracted to the inlet 5 iflhich they snapped at occasionally. However j 

 they did not mill around the inlet^ bat rather increased their cruis- 

 ing speed once they sensed the clear extract „ It should be emphasized 

 that this clear extract was invisible in the tanko 



After h^ minutes, during which period the fish became calm and 

 resumed their normal cruising speed^^ the murky portion was introducedo 

 In the experiment recorded in figure Tj the tunny's speed was high 

 during the first minute of siphoning but decreased thereafter o Fr-om 

 this and other experiments it was concluded that the murky portion 

 had no apparent effect on the cruising speed of either the yellowfin 

 or the tunr^o Both species^ however^ were attracted by the whitish 

 color of the murky extract and by the shreds of flesh contained in it. 

 They snapped at the shreds but did not swallcvj them This attract- 

 ion is indicated by the increased number of passes across AB in Tests 

 36 to Uo„ 



Co One experiment using clear and murky extracts of skipjack 

 flesh (120 grams) was performed after the fish had been recently fedo 

 Neither the cruising speed nor the number cf passes gave any indica- 

 tion of a positive attraction = This was expected from observations 

 of their feeding activity in the tanko On thromng food to -^hem, at 

 first they take it greedily ^ milling around at increased speed,, soon 

 they r'eact more slowly as their hunger is satisfied^ finally they 

 ignore tlie foodo 



Do Since it v/as established that the clear extract contains the 

 attractive factor(s)j an attempt was made to determine whether this 

 was contained in the "fat" (petrol ether soluble) or "protein" 

 (residual) partso The fat fraction was obtained by shaking the clear 

 extract with petrol ether and separating the latter fiom the residue 

 or protein fraction,. After evaporation of the petrol ether in the 

 refrigerator (where the protein fraction was also stored during the 

 period of evaporation) the fat extract was suspended in the same 

 amount of distilled water as that of the protein fraction,. Both frac- 

 tions v/ere diluted with seawater to 3 liters In the experiments 

 which are discussed below^, one yellowfin and five tunny were present. 

 All fish tended to school together, with the yellovrfin trailing o 



In one experiments the results of which are shonrn in figure 8, 

 yellowfin flesh (200 grams) was used.^ yielding 350 cubic centimeters 

 of the clear portion. This was shaken with 75 cubic centimeters of 

 petrol ether o During the preliminary trials^, the fish appeared to be 

 h\xngry, and were excited by the presence of the observer » The protein 

 fraction was siphoned in firsto D^iring the first 2 minutes there was 



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