FISH FLESH EXTRACTS 

 SKIPJACK 

 BIGEYE 

 YELLOWFIN 

 OTHER FISH 



FISH VISCERA, BLOOD, a SKIN EXTRACTS 

 TUNAS 

 OTHER FISH 



TUNA FISH MEAL S STICKWATER EXTRACTS ■ 



OTHER ANIMAL EXTRACTS 



ORGANIC CHEMICALS 



MISCELLANEOUS 



^ ATTRACTION 



12 NO ATTRACTION 



n TESTS OF CHEMICAL 



'—' FRACTIONS 



_1_ 



J_ 



J_ 



J_ 



J_ 



J_ 



_J_ 



10 20 30 40 50 60 70 80 90 100 110 120 

 NUMBER OF EXPERIMENTS 



Figure 23. Search for Bait Substitutes. A major pro- 

 ject of our laboratory is a search for live bait substitutes. Rather 

 than trying various things in hit=or-miss fashion, we have been 

 making controlled experinnents on tuna held in a pond at the Uni- 

 versity of Hawaii Marine Laboratory at Coconut Island to find out 

 whether they use sight, taste, smell, hearing, or combinations 

 thereof, to locate food„ In 1951 we found that tuna were sensitive 

 to extracts made from the tissues of fish. In 1952 the taste^smell 

 experiments were extensive as shown in the above chart. Early 

 in 1953 we began to test the extracts on tuna schools out at sea. 

 Results have been disappointing. It probably will be necessary to 

 combine visual and chemical stimuli to attract and hold the fish 

 near the stern of the vessel for pole and line fishing. 



24 



