Between 2001 and 2008, more than 3,000 scat samples were collected for prey studies. Preliminary processing (washing) of the samples was carried out on the research vessels and frozen samples were then sent to NMML or the Alaska SeaLife Center. Preliminary results indicate that in Russia the diet of Steller sea lions consists of at least 83 prey types (50 of which have been identified to species).
According to the frequency of occurrence, the top 10 species are Atka mackerel (Pleurogrammus monopterygius), walleye pollock (Theragra chalcogramma), Pacific salmon (Oncorhynchus spp.), sculpins (Cottidae), cephalopods, Pacific sand lance (Ammodytes hexapterus), Pacific herring (Clupea pallasii), northern smoothtongue (Leuroglossus schmidti), snailfish (Liparidae), and Pacific cod (Gadus macrocephalus).
Plotting the results of the cluster analysis by geographic location resulted in seven distinct geographic areas of prey similarity: northern Kamchatka Peninsula, southern Kamchatka Peninsula, Commander Islands, northern Kuril Island rookeries, northern Kuril Island haulouts, southern Kuril Islands, and the northern Sea of Okhotsk.
There was no significant relationship between diet diversity and rookery population trends. For example, the southern Kuril Islands had the highest level of diet diversity but had a relatively stable population trend, whereas, the southern Kamchatka Peninsula had the second highest level of diet diversity but also the second highest level of population decline.
The 10 most common prey items consumed by Steller sea lions in the Russian Far East were similar to those consumed by the western stock in Alaska waters; however, the proportions consumed were significantly different. This difference is primarily due to the greater occurrence of sculpins in the Russian sea lions' diet.
