Loughlin et al : Diving behavior of immature Eumetoplas jubatus 



577 



80% 



70% 



60% 



S 50% 



Z 40% 



g 30% 



20% 



10% 



0% 



B 



I- c e f g h 



21 00-259 



3:00-8:59 



^iMt^ 



a b c rt o ' g 



9:00-14:59 



a D c d p f g 



15 00-20:59 



Period 

 Figure 6 (continued) 



pears to concentrate in the deep nearshore 

 channels and gulhes of the Gulf of Alaska 

 (Sinclair and Zeppelin, 2002). 



The differences in dive depths that we re- 

 port also could be typical of the variability 

 among individuals. Boveng et al. ( 1996 ) ana- 

 lyzed TDR data for six dive-related variables 

 and found that dive duration was the least 

 variable and vertical distance (dive depth) 

 was the most variable among individual 

 Antarctic fur seals (Arctocephalus gazella ). 

 In our study, there was high individual vari- 

 ability in both dive depth and maximum 

 depth and little variability in dive dura- 

 tion — results similar to those of Boveng et 

 al.'s (1996) study 



A female Steller sea lion nurses her pups 

 during the day, stays with the pup for the 

 first week, then goes to sea on foraging trips. 

 Maternal pup-attendance patterns seem to 

 vary over the sea lion's geographic range; 

 the average range of time for foraging trips 

 during lactation are from about 24 h to 2 d at 

 the southernmost rookery at Aho Nuevo Is- 

 land, California (Higgins et al., 1988; Hood and Ono, 1997; 

 but note that some of this variability may have been the 

 result of El Nifio conditions during part of the Higgins et 



 Alaska YOV 

 DAIaska yearling 



 Washington yearling 



Period (local time) 



Figure 7 



Percentage of dives occurring in each time bin for Alaskan young-of-the-year 

 ( YOY), Alaska yearling, and Washington yearling Steller sea lions. Twenty- 

 five animals are represented from 1994 to 2000. 



al. study period), about 25 h at Lowrie Island, 19 h at Fish 

 Island, 11 h for Chirikof Island, and 7 h in the Aleutian 

 Islands (Brandon, 2000). 



