Characterizing the winter movements and diving behavior of subadult Steller sea lions (eumetopias jubatus) in the north-central Gulf of Alaska

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Title: Characterizing the winter movements and diving behavior of subadult Steller sea lions (eumetopias jubatus) in the north-central Gulf of Alaska
Author: Briggs, Holly Beth
Abstract: Recent studies indicate a 70 % decrease in the Alaskan Steller sea lion (SSL ) population (ca . 5 % per year ) since the early 1980's . In accordance with a 1997 status classification of the Western Steller sea lion (WSSL ) stock as endangered , the "critical habitat" for the species was to be defined . This habitat has now been designated to include 10 -20 nautical mile buffer zones around most rookeries and haulouts in the Gulf of Alaska (GOA ) and Aleutian Islands . However , these zones were based on limited , summer , foraging data . The primary objective of this study was to characterize juvenile SSL diving behavior and habitat use along the Kenai Peninsula and Prince William Sound (PWS ) from winter to spring . Fifteen free ranging , subadult SSL of both sexes were captured and equipped with satellite telemeters at five haulout sites in PWS and Resurrection Bay , Alaska . Telemeters transmitted for an average of 122 days (range 38 -181 days ) . A total of 11 ,692 locations were received and 217 ,419 dives recorded . All sea lions exhibited localized movements parallel or close to shore (3 -15 km offshore ) . Young of the year (YOY ) exhibited high site fidelity . Older juvenile sea lion lions were less restricted in their movements and traveled greater distances (200 -400km ) visiting a variety of islands , buoys , and other locations in PWS . Most dives were short (mean duration = 1 .1 min ) and shallow (mean depth = 10 .8 m ) , with animals diving to an average maximum depth of 193 m . During winter (January and February ) , many dives ( >40 % ) occurred during the daytime (0900 -1500 LT ) . However , by April and May this pattern shifted and the animals made most of their dives ( >40 % ) during the night (2100 -0300 LT ) . This relationship was more pronounced for dives deeper than 20 m and coincided with the seasonal increase in photoperiod . Subadult SSL , especially YOY , remained within the 20 nautical mile coastal zone during winter and spring . Shallow , nearshore waters provide important habitat during this critical period of transition to nutritional independence . However , more conclusive data on SSL foraging ecology is necessary to better understand locations and depths preferred by the species .
URI: http : / /hdl .handle .net /1969 .1 /5028
Date: 2007-04-25

Citation

Characterizing the winter movements and diving behavior of subadult Steller sea lions (eumetopias jubatus) in the north-central Gulf of Alaska. Available electronically from http : / /hdl .handle .net /1969 .1 /5028 .

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