400 



200 



NUMBER CAUGHT PER SCHOOL 



Ol— *- 



4i — r- 



WEIGHT CAUGHT PER SCHOOL 



"1 1 1 1 1 1 



AMOUNT OF BAIT USED PER SCHOOL 



FISHING DURATION PER SCHOOL 



Ol 1 L. 







200 



T i 1 1 J r 



AVERAGE SIZE 



Fishing duration . --Fishing ends either when 

 the captain decides to abandon the school or 

 when the school breaks away from the vessel. 

 We defined fishing duration as the elapsed time 

 from the landing of the first fish to the end of 

 fishing and for 617 schools found that, although 

 ranging widely from 1 to 155 minutes, it was 

 usually short. The distribution of fishing dura- 

 tion (table 10 and fig. 9), grouped into 5-minute 

 intervals, peaked at 6-10 minutes, with pro- 

 schools fished at longer 



fewer 



gressively 

 durations. 



Biting behavior 

 fishing duration, 

 percent of the 

 because biting 



has a strong influence on 

 . The captains abandoned 42 

 schools after fishing started, 

 slowed to a point where they 



NUMBER OF SCHOOLS 



i 



I 23456789 10 



MEN FISHING (NUMBER) 

 Figure 8. — Relation between number of men fish- 

 ing per school and average values of catch per 

 school, amount of bait used per school, fishing 

 duration per school, and size of fish per school, 

 June-August 1967. 



could no longer justify further expenditure of 

 time and live bait (table 11). Moreover, they 

 abandoned an almost equally large percentage-- 

 40 percent--of the schools after biting stopped, 

 whereas they abandoned only 8 percent because 

 the schools sounded and failed to return to the 

 surface. In the remaining 11 percent of the 

 schools, the captains quit fishing when they 

 learned that the schools consisted of small fish, 

 when predators--shark or billfish--attacked 

 and dispersed the school, or when bait was 

 exhausted. 



It follows that biting behavior influences not 

 only fishing duration, but also the amount of 

 bait chummed to hold the school near the ves- 

 sel and the catch. Table 10 and figure 9 show 

 that the vessels usually used more bait and 

 caught more fish from good-biting schools that 



Table 10. — Number of schools and averages of catch per school, amount of bait used 

 per school, number of men hooking per school, and fish size, tabulated by fish- 

 ing duration per school for seven Hawaiian skipjack tuna vessels, June-August 

 1967 



Fishing duration 



Schools 



Catch 



per school 



Bait used 



3er school 



Men hooking 



Fish siz( 



Minute 



Number 



Number 



Metric ton 



Bucket 



Number 



Kg.- 



1-5 



63 



29.3 







1 



1 



.5 



6 



2 



3.2 



6-10 



88 



62.3 







3 



2 



.1 



6 



6 



4.2 



11-15 



82 



106.7 



0. 



5 



2 



.7 



6 



9 



4.7 



16-20 



70 



122.0 



0. 



8 



3 



.5 



6 



9 



6.9 



21-25 



68 



140.0 



0. 



9 



3 



.8 



6 



8 



6.4 



26-30 



59 



151.1 



1. 



3 



4 



.9 



6 



9 



8.5 



31-35 



39 



187.8 



1. 



4 



5 



.2 



6 



7 



7.6 



36-40 



37 



220.7 



1. 



9 



5 



.7 



6 



9 



8.7 



41-45 



20 



222.1 



2. 



3 



6 



.8 



6 



9 



10.5 



46-50 



17 



204.9 



1. 



7 



5 



.7 



6 



8 



8.2 1 



51-55 



11 



257.6 



2. 



5 



8 



.3 



7 



1 



9.8 i 



56-60 



11 



277.7 



2. 



2 



6 



.4 



7 



3 



7.9 



>60 



52 



379.8 



2. 



9 



10 



.4 



7 



3 



7.8 ' 



14 



