Results 



Some 40 experiments were conducted with Inedible objects and drag luj?es. 

 Including those with and without the use of extract. Typical results for some of 

 those in which the response was measured are included in table 5. 



There was no noticeable response to the strips of red cellophane or the 

 mica flakes. The squares of alumlniun foil produced a momentary attraction to the 

 chvmuned fish, but would not hold them. 



The tin strips and trlamjles , which gyrated and flashed in the water as 

 they sank, were temporarily attractive to the fish. V/hen a school was chvumned to 

 the stern with live bait, individual tuna could be momentarily lured from the stem 

 to amidships by chumming with strips or triangles of tin from the latter location. 

 This was repeated on several occasions. However, having investigated the flashing 

 tin, the skipjack would return to the stern to feed on live bait. Of 57 skipjack 

 caught from one school during such experiments, 2 had one strip of tin apiece In 

 the stomach. In some tests, when chumming with live bait was replaced by chumming 

 with tin strips from the stern, the fish remained with the ship for a slightly 

 longer period than when no chum was used, but they followed the strips of tin as 

 they sank and therefore kept beyond the reach of the poles. 



The calcium carbide pellets gave off bubbles of acetylene gas when thrown 

 into the water, along with a milky precipitate which streeuned behind the pellets as 

 they sank. This visual stimulus seemed to attract the fish and hold them for a 

 short period of time. However, no pellets were found in the stomachs of fish which 

 were caught, and no dead or distressed fish were noted In the fishing area after 

 chumming with this active chemical. 



The addition of extracts when chumming with visual lures did not seem to 

 cause any added excitement or attraction. 



The lure array, either without or with the addition of extract, did not 

 seem to attract the schools when towed near them. However, it was difficult to 

 keep up with the schools when the array was being towed; usually the schools 

 managed to keep ahead of the ship. As shown by data included in table 5, towing 

 the lure array close to the stern after the fish had been chummed with live bait 

 did not seem to hold them for any additional period of time beyond that of the 

 controls . 



Discussion 



Obviously little success was achieved in attracting and holding schools 

 of tuna with Inedible lures of the types which were used. The observation that 

 the tuna will respond to some extent to shiny objects such as strips of tin, sil- 

 very objects such as squares of aluminum foil, and effervescing objects such as 

 wet calcium carbide pellets is of interest and possible value in devising other 

 artificial liores. The results suggest that the sense of vision is of major im- 

 portance in the feeding of tuna in their natural environment. 



SEA TESTS WITH EDIBLE LURES 



Materials 



The preparation of edible lures, consisting basically of gelatin cap- 

 sules, macaroni, and agar, has been described In a previous section. There was 

 no opportvinity of testing the gelatin capsules at sea. Several tests were per- 

 formed with the non-motile, edible, macaroni and agar preparations. In addition 

 experiments were performed with dead anchovy, cut-up preserved herring, and strips 

 of skipjack flesh, both without and with the addition of extract. 



16 



