from a iisliing boat), whereas they did react quite -strongly to ex- 

 tracts of tuna flesh. This attraction was based on chemical stimu- 

 lation rather than on sighto as proven by experiments with the clear, 

 centrifuged portion of the tuna flesh preparation in which the invisi- 

 ble fluid attracted the fisho 'fhe tuna were attracted to the debris 

 by sight, but they did not accept the particles as foodj, even when 

 taken into the mouths It was shown that an extract equivalent to 5 

 grams of tuna ilesh m J liters of seawater^ siphoned into the tankj 

 was sensed by the tunny j, and that in one experiment^ at least^ an 

 extract equivalent to 25 grams of tuna flesh in 3 liters of seawater 

 was positively attractive to both yellowfin and tumiyo Extracts of 

 marlin flesh also gave positive reactions^ showing that the response 

 in the tuna flesh experiments was not conditioned by the fcodo 



Experiments with "fat" and "protein" fractions of the aqueous 

 extract of tuna flesh showed that the attractive substance was in the 

 lattero This is in contradiction to the results of Allison and Cole 

 Cl93U) who found that fatty acids had an effect on both freshwater 

 and marine fisheSo It must be left for future research to determine 

 what part of the protein-containing fraction is the actual attract- 

 anto Von Frisch's (19U1) experiments might be recalled in this con- 

 nectiont, suggesting that such substances might be purm- or pterin- 

 likeo 



The tuna displayed no positive reaction to either asparagine or 

 dol-asparagine solutions o 



Experiments with copper acetate, a well-known shark repellent 

 (V/hitley and Payne 19hl) showed that this substance has a repellent 

 action on tunas o However, they were not as sensitive to this chemi- 

 cal as other fish (manini and baitfish) which were also present in 

 the tanko Only a few experiments with relatively weak solutions 

 were conducted because of danger of harming the tunao 



It should be emphasized that the experiments were conducted with 

 tuna in captivity^ rather than in their normal habitat, and that the 

 reactions in the latter might be different „ It should also be empha- 

 sized that when both yellowfin and tunny are present in the tank, 

 there is an interaction which affects both cruising speed and school- 

 ing pattemo For this reason, caution must be exercised in comparing 

 the intensity of the reactions of the two specieso In general,, how- 

 ever, the reactions of the tunny seemed to be considerably more pro- 

 nounced than those of the yellowfin, indicating a greater sensitivity 

 to the attractive substances o 



32 



