NOTE Polovina et al.: Dive-depth distribution of Carretta carretta and Lepidochelys olivacea in tine central North Pacific 



191 



Loggerhead 225 M(DH) 



20 



2100-0300 

 0900-1500 



— IhDl I I I I 



E, (III (i: 4 0.6 8 I II 



Loiijzerfiead 24747 (LH) 



20 



80 



120 



'^=-^ 



2100-0300 

 0900-1500 



no II ; 4 6 o« in 



no n : 0,4 0.6 OS i o no n: 4 n6 on in 



Cumulative frequency 



Figure 2 



Time-at-depth cumulative frequency distributions for day (0900-1500 h) and 

 night (2100-0300 h) periods for each of the four turtles. The 100 m reference 

 depth is noted with a dashed line. DH indicates that the turtle was released with 

 the hook deeply ingested, LH indicates that the turtle was lightly hooked and 

 released with the hook removed. 



depth and dive-depth distributions pooled over the four 6- 

 hour time periods by species. The time-at-depth frequency 

 distribution showed that the loggerhead sea turtles spent 

 about 40% of their time in the top meter and virtually all 

 their time shallower than 100 m(Fig. 3). We also examined 

 the frequency distribution of the maximum depth of each 

 dive and the deepest dive in a 24-hour period. The cumula- 



tive distribution of maximum depth of each dive indicated 

 that most dives were very shallow: 70'"r of the dives were 

 no deeper than 5 m ( Fig. 3 ). The cumulative distribution of 

 the maximum dive depth achieved over a 24-hour period 

 indicated that for approximately S'/f of the days, a dive 

 exceeded 100 m (Fig. 31. Status messages reported that the 

 deepest daily dive recorded was 178 m. 



