580 



Fishery Bulletin 101(3) 



estimated maximum dive depth values differed by large 

 amounts (e.g. sea lion PTT 14071), perhaps because the 

 deployment period was brief, before deep dives occurred. 

 For others (e.g. PTT 14074) the difference may have been 

 due to the young animal's continued dependence on the 

 female for nourishment; deeper dives do not occur until 

 weaning. In addition, we note that our dive duration data 

 were stored in bins of 1-min intervals (from 1 to 6 min in 

 the early instruments and from 1 to 14 min in the recent 

 ones); the exact duration of each dive is unknown. 



Movement patterns also suggest that the swimming 

 ability of juvenile sea lions is comparable to that of adults. 

 It is not unusual for young sea lions to travel distances as 

 great as 1784 km from the natal rookery; as they approach 

 adulthood they generally remain within 500 km of their 

 natal rookery (Raum-Suryan et al., 2002). In our study 

 some young sea lions traveled several hundred kilometers 

 between sites while presumably searching for food or ven- 

 turing from the natal rookery site. 



Further analysis of our SDR data is warranted to more 

 fully understand sea lion diving behavior and its relation- 

 ships with oceanographic parameters, daily and season 



change, and behavioral features as discussed by Fedak et 

 al. (2001). The time allocation at depth (TAD) index de- 

 scribed by them will be a useful method for interpretation 

 of our SDR (and TDR) data. Further analysis of our SDR 

 data is needed to determine if such a study is possible. 



Acknowledgments 



Field assistance was provided by numerous NMML staff; 

 logistical support was provided by Alaska Helicopters and 

 the captain and crew of the U.S. Fish and Wildlife Service 

 research vessel Tiglax. The manuscript was improved by 

 comments from D. DeMaster, G. Duker.T. Gelatt, R. Hobbs, 

 M. Lander, J. Lee, R. Ream, E. Sinclair, and two anonymous 

 reviewers. 



Literature cited 



Baba. N., H. Nitto, and A. Nitta. 



2000. Satellite tracking of young Steller sea lion off the coast 

 of northern Hokkaido. Fisheries Sci. 66:180-181. 



