770 



Fishery Bulletin 100(4) 



Time (CTZ) 



00 12 00 12 00 12 00 12 00 12 00 12 00 12 00 



I _ . '''' ,. ' ,. '''' , ''■ I 28 



400 



12 00 12 00 12 00 12 00 12 00 12 00 12 00 12 





 50 - 

 100  

 150  

 200 

 250  

 300  

 350 

 400 



■23 



- 14 



- 14 

 -13 

 -13 

 -12 



11 

 10 



Figure 1 



Depth and temperature records for bigeye tuna carrying archival tags after 

 release and before recapture at FADs. (A) Bigeye tuna 99-874. The arrow 

 represents the time the FAD was removed. (B) Bigeye tuna 99-835. The 

 arrow indicates the time the set was made by a purse-seine vessel at the 

 FAD. CTZ = central time zone. 



Unassociated type-2 behavior 



Type-2 behavior was defined as the behavior offish that did 

 not undergo the diel shifts in swimming depths at dawn 

 and dusk but remained at depths in excess of 50 m for more 

 than 16'7f of the time during a 24-h period (Fig. 5). The 

 percentage of total days classified as type-2 behavior for 

 individual fish ranged from 1.5'/f to 49.9'? (mean=27.7'7f , 

 95*7^ CI=6.2Vf ). The mean duration of type-2 behavior for 

 individual fish ranged from 0.4 to 7.3 d (grand mean=3.3 d, 

 95% CI=0.8 d) (Table 2). The distribution of the durations 

 for each of the 245 tvpe-2 behaviors is shown in Figure 3B. 



Behavior associated with floating objects 



Behavior associated with floating objects was defined as the 

 behavior of fish that remained below 50 m for no more than 



16'7f of the time throughout a 24-h period (Fig. 6). Although 

 bigeye tuna mostly remained in the mixed layer while asso- 

 ciated with floating objects, there was, nevertheless, a prom- 

 inent diel cycle in the average depth distribution — from 

 shallower at night to slightly deeper during the day (Fig. 

 6). The mean swimming depths for the data illustrated in 

 Figure 6 are 27.7 m at night and 33.5 m during the day. The 

 percentage of total days classified as associated behavior for 

 individual fish ranged from 1.39', to 39.0% (mean=:18.7%, 

 95% CI=4.0%). The mean duration of associated behaviors 

 for individual fish ranged from 0.5 to 7.5 d (grand mean=3.1 

 d. 95% CI=0.6 d) (Table 2). The distribution of the durations 

 of the 140 associated behaviors is shown in Figure 3C. 



An examination of the classification of daily behavioral 

 types by individual fish sorted by lengths (Table 2) indi- 

 cated that a greater percentage of time was spent at FADs 

 by bigeye tuna less than 110 cm in length (mean=23.3%, 



