The material was sensed very quickly by the tunny and produced a 

 typical response, with all components, in the vicinity of the outlet. 

 The response was maintained during the entire time necessary to 

 siphon in the material A few fish would leave the area and dash down 

 the pond, but they would invariably return to the area of greatest con- 

 centration. After all the material had been siphoned in, the response 

 quickly decreased until finally, after about 18 minutes, normal 

 swimming was resumed. 



Flesh Extracts of Other Fish 



Positive responses were obtained not only to extracts of 

 tuna flesh, but also to extracts of aholehole flesh (Nos. 49, 99, and 

 105), jach or ulua flesh (No. 96), and barracuda flesh (No. 98)„ There 

 was no response to wahoo or ono flesh (No. 6), but the fish were not 

 behaving well in this early tank experiments It is evident that an at- 

 tractant is present in at least some of the white-fleshed fish, as well 

 as in the red-fleshed tuna. We gained the impression that the response 

 was generally less in these flesh extracts than in those from tuna, but 

 this cannot be proved because of thefew experiments conducted with 

 the former, variation in the quantity of material used, and the great 

 variability in the strength of the response. In most of the compar- 

 isons the response appeared less (compare Nos. 49 and 50, 96 and 97, 

 97 and 98, 105 and 106) but in one it was greater (97 and 99). Van Weel 

 (1952) obtained only a weak response to white-fleshed anchovy or nehu 

 ( Stolephorus purpureus ) extract. 



Extracts of Tissues Other than Flesh 



Strong responses, ranging from XXXX to X, were obtained 

 with extracts of unsegregated skipjack viscera treated in several dif- 

 ferent ways (Nos. 137, 139, 141, 145, 146, 219, 220, 221, 236, 264, 

 279, 352, 353, 356)„ 



Excellent responses were also obtained with extracts of 

 skipjack blood (Nos. 43, 70, 95), yellowfin blood (No. 23), and tunny 

 blood (No, 30). Jack or ulua blood (No. 94) gave a positive though 

 weaker response. In contrast to these results beef blood, either whole 

 (Nos, 55 and 74) or the plasma portion (No. 6l), was not attractive. 

 In fact, whole beef blood, of a deep red color, was avoided by the tunny 

 in both the tank and the pond experiments- -a repellent effect which was 

 probably visual in origin. 



Excellent responses were obtained with extracts of yellow- 

 fin liver (No, 25) and tunny liver (No, 28), 



32 



