776 



Fishery Bulletin 100(4) 



Time (CTZ) 

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



22 00 02 04 06 08 10 12 14 16 18 20 22 00 02 





 100 

 200 

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 400 

 500 

 600 

 700 

 800 

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 1000 



-.^yUrAM^Jrt-U'lj-jj^.jiiiUuJ^ 



-^-^fljvi;ju 



May 16,2000 



15 



- 13 



- 12 



- 10 



25 



Figure 7 



Depth and temperature records for a bigeye tuna carrying an archival tag 

 (99-792). exhibiting deep diving behavior Approximate area, 1°S 97°W, is 

 based on geolocation estimates from the archival tag. CTZ = central time 

 zone. 



was spent above 50 m at night and between 250 to 300 m 

 during the day. From April to June, the average depths of 

 the 20°C and 15°C isotherms were 50 and 100 m, respec- 

 tively. The habitat selected by the fish during July, August, 

 and September was different and more variable during 

 the day than that for the previous three months. Most of 

 the time was spent above 50 m during the night. During 

 the day the primary mode in depth in July was similar 

 to the previous three months, but in August the primary 

 mode shifted to about 200-275 m. In July the average 

 depths of the 20°C and 15°C isotherms were 17 and 90 m, 

 respectively, whereas in August and September the aver- 

 age depths of the 20°C and 15°C isotherms were 10 and 

 75 m, respectively. In September the depth distribution 

 during the day was more uniform from about 100-350 

 m, with a slight mode between 175 and 250 m. The daily 

 vertical behavior of the fish during September was highly 



unusual and erratic in relation to previous months and 

 to October; TSVe of the days for five fish were classified 

 as unassociated type-2 behavior. The habitat selected by 

 the fish during October, November, and December was 

 different during the night, than that for the previous six 

 months. Most of the time was spent above 25 m during the 

 night. During the day the primary modes in depth during 

 October, November, and December were not as distinct 

 as in previous months, excluding September, but were 

 primarily between 150 and 275 m. The average depths of 

 the 20°C and 15°C isotherms for October and December 

 were 15 and 75 m respectively, whereas in November the 

 average depths of the 20°C and 15°C isotherms were 25 

 and 50 meters, respectively. The habitat selected by the 

 fish during the day in January, February, and March was 

 similar, with a distinct mode in depth between about 

 200 and 300 m. During the night, there was a transition 



