Abstract
The diet of Steller sea lion Eumetopias jubatus was studied based on undigested food parts found in feces collected in the summer season on 20 rookeries in the Russian Far East. A total of 915 samples were analyzed between 2004 and 2008, in which 65 food items were identified. The frequency of occurrence of 11 diet items was greater than 5%, including Atka mackerel Pleurogrammus monopterygius (64.8%), Pollock Theragra chalcogramma (44.3%), Pacific salmon Salmonidae (20.5%), Irish lord Hemilepidotus sp. (20.4%), Pacific sand lance Ammodytes hexapterus (15.8%), Pacific herring Clupea pallasi (9.5%), Squid and Octopus Cephalopoda (8.4%), Pacific cod Gadus macrocephalus (5, 9%), Pacific sandfish Trichodon trichodon (5.9%), Flatfishes Pleuronectidae (5.8%), Threespine stickleback Gasterosteus aculaeatus (4.9%). Three regions with different diets were identified – the Sea of Okhotsk, the Kuril Islands, and Kamchatka with the Commander Islands. In the Sea of Okhotsk, Pollock and Herring (83.6% by frequency of occurrence) dominated among undigested food remains in feces. The diet at the Kuril Islands rookeries was variable within the region. The general pattern was a low diversity of diet at each Kuril Island sites and predominance of 1-3 food items, probably the most accessible near the sites (Pollock, Squid and Octopus, Atka mackerel, Pacific salmon). The diet pattern in Kamchatka and the Commander Islands in the summer season was characterized by a high diet diversity. In contrast to other regions, the diet includes in high proportion small non-commercial species – Sand lance, Irish lord, Pacific sandfish, Flatfishes, Threespine stickleback and others. The regional patterns of sea lion diets show the spatial distribution and areas of abundant biomass of the main food items. The diet patterns of sea lions from rookeries differed from haulouts in having a higher content of abundant food items. Long-term changes in diet structure were not statistically significant.
Highlights
Камчатский филиал Тихоокеанского института географии ДВО РАН, г
Статья поступила в редакцию 10.09.2021; принята к печати 21.09.2021 ов ик ан Исследовано питание сивуча Eumetopias jubatus по непереваренным остаткам пищи в экскрементах, собранных в летний сезон года на 20 лежбищах Дальнего Востока России
The frequency of occurrence of 11 diet items was greater than 5%, including Atka mackerel Pleurogrammus monopterygius (64.8%), Pollock Theragra chalcogramma (44.3%), Pacific salmon Salmonidae (20.5%), Irish lord Hemilepidotus sp. (20.4%), Pacific sand lance Ammodytes hexapterus
Summary
Для анализа использовали только присутствие или отсутствие объекта питания в пробе, размер потребляемых сивучем рыб в анализе не учитывался. Относительная «важность» объектов питания в рационе была основана на частоте встречаемости (FO), которую рассчитывали как отношение количества проб, содержащих определенный объект питания, к общему количеству проб [28]. ∗ 100, FO – частота встречаемости объекта питания i; ni – число проб, содержащих объект питания i; nt – общее число исследуемых проб выборки t. Однако сумма частот встречаемости отдельных объектов питания превышает 100%. В связи с этим нами был применен еще один индекс – модифицированная частота встречаемости объектов питания [26]. Определяли число объектов питания, обнаруженных в 1 пробе, и рассчитывали медиану значений с квартилями (q0,25; q0,75; N);. По указанным выше причинам используемый нами метод исследования питания позволяет лишь установить видовой (качественный) состав диеты и относительное обилие видов в питании сивуча. Все статистические процедуры были выполнены в среде R (http://www.R-project.org)
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