Trites et al.: Diets of Eumelopios jubatus in Southeast Alaska 



235 



whales if they had to forage for longer 

 periods of time. 



Population trends in Southeast Alaska 

 have been opposite to those observed 

 in the Gulf of Alaska (Trites and Lar- 

 kin, 1996; Calkins et al., 1999; Pitcher 

 et al., 2007). The robustness of the 

 Southeast population compared to the 

 other regions of Alaska may reflect a 

 difference in diet. One explanation for 

 this finding is that Steller sea lions in 

 Southeast Alaska eat a wider range of 

 prey and therefore have a more diverse 

 diet. Another is that low energy-density 

 prey (such as pollock) do not comprise a 

 significant portion of the sea lion diet in 

 Southeast Alaska. 



Our goal was to determine the diets 

 of Steller sea lions in Southeast Alaska. 

 We sought to test two hypotheses: 1) diet 

 in Southeast Alaska is the most diverse 

 of all regions inhabited by Steller sea 

 lions; and 2) pollock is not an important 

 prey species in Southeast Alaska. We 

 also wanted to document prey associa- 

 tions and seasonal changes in diet. 



Materials and methods 



There are three major breeding areas 

 (rookeries) and over 45 major non- 

 breeding areas (haulouts) in Southeast 

 Alaska. We collected 1494 scats from 

 12 haulouts and all three rookeries 

 from 1993 through 1999 (Fig. 1). Some 

 areas, such as the Forrester rookery, 

 were sampled every year, and others 

 were sampled less frequently (Table 1). 

 We grouped our analyses into rookeries 

 and haulouts, and then into subgroups 

 by sample size, location, and frequency 

 of sampling. Haulouts consisted of 12 nonbreeding sites 

 in the inside protected waters of Southeast Alaska ( Fig. 

 1). Rookeries consisted of the three breeding areas in 

 Southeast Alaska (Forrester Island, Hazy Island, and 

 White Sisters Islands). 



Scats were generally collected opportunistically, when 

 rookeries and haulouts were disturbed in order to count 

 pups or for other research purposes. Each scat was 

 placed in a zip-lock plastic bag and frozen in a 5-gal- 

 lon plastic bucket before it was shipped to the Food 

 and Energy Consumption Laboratory at the Vancouver 

 Aquarium Marine Science Centre for cleaning. Only 

 scats that were big enough or solid enough to likely 

 contain prey remains were collected, and only one scat 

 was collected from any group of scats if there was any 

 doubt about whether the scat came from more than one 

 Steller sea lion. Each thawed scat was transferred to a 

 plastic jar and soaked in water for 1-6 days. Periodic 



Figure 1 



Major rookeries (White Sisters, Hazy Island, and Forrester Island) and haul- 

 outs (all other sites) of Steller sea lions (Euinetopias jubatus) in Southeast 

 Alaska during 1993-99. Labeled sites indicate where scats were collected. 



shaking of the jars ensured that the scats broke down 

 and formed a uniform slurry at the bottom of the jar. 

 Volume was recorded from graduated markings on each 

 jar. An elutriator removed most of the water-soluble 

 elements (Bigg and Olesiuk, 1990) before the remaining 

 sample was washed through a fine mesh screen. 



Prey species were identified at Pacific IDentifications 

 Inc. (Victoria, BC) from cleaned and dried hard parts; 

 the types of hard parts that were present and the spe- 

 cies from which they came were also noted. Prey hard 

 parts recovered from scats were compared with hard 

 parts from a reference collection of identified skeletal 

 and nonskeletal hard parts. Otoliths and all other hard 

 parts were identified to the lowest possible taxon. Hard 

 parts that were digested beyond recognition or were 

 not diagnostic for prey taxa were not included in our 

 analysis (e.g., ribs). Some recovered structures, such 

 as otoliths or squid beaks, could be used to estimate 



