Table 3. --Catch rates of bait and skipjack tuna in Hawaii, 1952-53 



fishing and hence the catch of tuna per unit 

 quantity of bait used. 



Catches made within 1 or 2 days after baiting 

 were usually larger than those made after bait 

 was held for a longer period. Data for Vessel 

 A for 1952-53 and for Vessel B for 1953 (the 

 night bait catch for Vessel B appeared to be 

 only partially recorded in 1952) showed that 

 the longer the bait was held aboard, the smaller 

 were the average catches of tuna. Exceptions 

 were the catches made during the same day on 

 which bait was taken and the catches made the 

 day after night bait was captured (fig. 1 and 

 table 4). After 3 days it is likely that the quan- 

 tity of bait still aboard may be insufficient to 

 provide a major catch, although occasionally 

 enough bait may be left to tempt the fisherman 

 to go fishing again. About 10 percent of the 

 total number of fishing trips occurred after 3 

 or more days since the last catch of bait. 



The catch of skipjack tuna per trip per kilo- 

 gram of live bait expended was highly variable; 

 for Vessel A during 1952-53 it ranged from 

 to more than 113 kg. The higher value is un- 

 doubtedly not a maximum because the data 

 were not adjusted for baitfish mortalities. As 

 might be expected, the distribution of this ratio 

 was highly skewed. Average seasonal values 

 were given in table 3 for Vessel A and Vessel B. 



As a working hypothesis, we assume that fish 

 bite better if they are hungry. Biting response 

 presumably changes with time, as the skipjack 

 tuna passes through periods of satiety and hun- 

 ger. A thorough understanding of the feeding 

 behavior and what may affect it could substan- 

 tially increase the efficiency of fishing. If the 

 fish pass through cycles of satiety and hunger. 



SAME DAY NEXT DAY 2d DAY 3() DAY 4lh DAY 5th DAY 6th DAY 



Figure 1. --Hawaiian skipjack tuna catch in 

 metric tons according to number of days 

 since bait catch was made. 



then it would be of tremendous value to the 

 fishermen to be aware of this periodicity and to 

 be able to detect the stages from the behavior 

 of the fish. If feeding follows a daily rhythm, 

 the fishermen could take advantage of this fact 

 by concentrating fishing effort in the "best" 

 periods. Data concerning skipjack tuna catches 

 and time of day, however, gave no evidence of 

 an optimum time for fishing; early mornings 

 and late afternoons were poor and catches ap- 

 peared to decline slightly at midday. It is not 

 clear whether this midday slump is due to 

 poorer fishing or to a slack in scouting inten- 

 sity while the crew is eating lunch.-' 



2/ 



— These data were from records of interviews 



with fishermen. 



