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Photoidentification In Avacha Gulf during 1999-2011 we identified 640 fish-eating killer whale individuals (including calves and newborns).
In the waters of the Commander Islands in 2008-2011 we identified additional 960 fish-eating killer whale individuals (including calves and newborns).
Analysis of the images revealed matches between the different regions: 123 individuals between Avacha Gulf and the Commander Islands, 26 individuals between Avacha Gulf and Karaginsky Gulf, 23 individuals between Avacha Gulf and Kronotsky Gulf, 26 individuals between the Commander Islands and Karaginsky Gulf, 33 individuals between the Commander Islands and Kronotsky Gulf, 6 individuals between the Commander Islands and Olyutorsky Gulf.
Mixing occurs between the studied areas of Eastern Kamchatka and the Commander Islands, but the amount on mixing varies for different areas. Between the coastal areas of Eastern Kamchatka from Avacha Gulf to Karaginskiy Gulf rather high rate of matches was found - apparently, killer whales in these areas belong to one community.
At the same time, at the Commander Islands we met a large number of whales that are not seen anywhere else. These facts suggest that a significant proportion of killer whales comes to the Commander Islands from some other non-investigated area. The most likely area is the western Aleutian Islands, geographically close and similar to Commander Islands by oceanographic parameters. In general, it seems that the Commander Islands are like a "crossroads" in the ways of killer whales from different regions, which explains the large number of identified animals, but the low frequency of between- as well as within-area matches. Thus only 29 from 108 killer whale groups encountered near Commander Islands (5-year period) were met during three and more days (maximum 6 days). Other 79 groups were met once or twice. At the same time 44 from 66 killer whale groups encountered in Avacha Gulf (8-year period) were met during three and more days (maximum 60 days) and 22 only once or twice.

 Social structure  We found out that fish-eating killer whales usually travel in stable groups, representing matrilinear units. No dispersion from a natal group was observed during the study. A total of 66 units were identified in Avacha Gulf.
Besides this, we also met killer whales similar to the mammal-eating orcas of the eastern North Pacific. These orcas were not encountered together with fish-eating ones.

 Foraging behavior  The main prey species for fish-eating killer whales in Avacha Gulf are different salmon species and Atka mackerel.
Mammal-eating killer whales were observed feeding only on a minke whale but other marine mammals can be their prey as well.

 Acoustic behavior  Observed killer whale groups proved to be highly vocal, producing sounds during most of the recordings. These sounds included discrete and variable calls, whistles and echolocation in different proportions. We have created the catalog of discrete calls of Kamchatkan orcas. With the acoustic analysis of vocal repertoires of different killer whale groups, we revealed 8 resident pods occurring in Avacha Gulf from year to year. All these pods shared at least one discrete call type, which means that all are members of the same clan. We named this clan “Avacha clan”.
We also identified two other clans - K19 and K20 clans which occur more rarely in Avacha Gulf but are more common at the Commander Islands.
All groups mentioned above correspond in appearance, as well as behavior and acoustic activity, to the fish-eating ecotype. Probable mammal-eating killer whales were recorded in Avacha Gulf only once. Calls of these whales differed from the dialects of all other groups ever recorded in Avacha Gulf, but were similar to the calls of mammal-eating killer whales from the Pacific coast of North America. During the recording we also heard distant (10-15 km) calls of fish-eating whales from the “Avacha clan”, but these whales showed no visible reaction to them.

 Genetics  Genetic analysis showed that most of our fish-eating orcas had SR-haplotype (like Canadian Southern residents and one clan of Alaskan residents). Genetic comparizon of fish- and mammal-eating killer whales showed that they belong to different populations.



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05 February 2019 01:00
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