Table 2. --Vessels and observers taking part in sea tests of tilapia, summer 1956 



Because of circumstances beyond the control of 

 the observers it was not always possible, how- 

 ever, to have the two baits used in a manner to 

 provide the desired information. Due to the 

 general excitement of the fishing operation when 

 the vessel was in contact with a school, and the 

 great desire of the fishermen to catch every 

 fish possible, the experiment was not always 

 conducted according to the design. On a few 

 days, as might be expected, no skipjack schools 

 were encountered. 



The results of each day's fishing are shown 

 in table 3 and sumnnarized in table 4. The data 

 are quite variable and difficult to evaluate. The 

 best fishing experienced during the tests was 

 that of the Neptune on May 22, when no tilapia 

 were used, and that of the Orion (fig. 4) on 

 June 21 and June 26, when we were furnished 

 with an excellent opportunity to compare the ef- 

 fectiveness of the two baits. On June 21 about 

 21, 000 pounds of skipjack were caught from two 

 schools at a rate of 9. 8 fish per minute and 30 

 fish per bucket of bait using nehu, as against 5.9 

 fish per minute and 12 fish per bucket of bait 

 using tilapia. On June 26, about 19,800 pounds 

 of skipjack were caught from five schools at the 

 average rate of 7.4 fish per minute and 31 fish 

 per bucket of bait using nehu, and 7. 6 fish per 

 minute and 23 fish per bucket of bait using tilapia. 



the two baits on a slow-biting school (upper 

 panel), and with a fast-biting school (lower 

 panel).i/ 



The fishermen remarked on the "hard- 

 bit i n g" quality of the skipjack schools when 

 tilapia were being used as bait. This biting be- 

 havior is a favorable reaction in the fishermen's 

 opinion since it is obtained with nehu during the 

 periods of best fishing. Other substitute bait 

 fish such as top minnows or mosquito fish 

 (Limia, MoUienesia , Gannbusia ) do not evoke 

 this response in skipjack and are not used by the 

 Hawaiian fishermen unless there is an extreme 

 scarcity of nehu. 



In the general sunnmary of the results (table 

 4) it is shown that 21 (56 percent) of the 37 

 schools first chun-imed with nehu surfaced and 

 responded to the bait; also that 10 (56 percent) 

 of the 18 schools first contacted with tilapia gave 

 a favorable response to the bait. Skipjack were 

 caught from 9 schools at the rate of 3. 5 fish per 

 minute and 12.2 fish per bucket of tilapia used. 

 This is not quite as good as the catch rate, 4.8 

 skipjack per nninute and 15. 3 per bucket of bait, 

 obtained with nehu from 23 schools, but there is 

 every reason to believe that, with experience , 

 chunnnners will learn to use the new bait more 

 effectively. 



When nehu and tilapia were employed in 

 fishing the same school, there was no noticeable 

 difference in the behavior of the skipjack when 

 the chummer switched from one bait to the other. 

 Figure 5 shows the variations in catch rate using 



— This method of depicting the catch rate 

 was devised by H. S. H. Yuen of POFI for use 

 in studying the biting behavior of skipjack schools. 



