Steller Sea Lion - Ecology

Ecology

The range of the Steller sea lion extends from the Kuril Islands and the Sea of Okhotsk in Russia to the Gulf of Alaska in the north, and south to Año Nuevo Island off central California. They formerly bred as far south as the Channel Islands, but have not been observed there since the 1980s. Based on genetic anаlyses and local migration patterns, the global Steller sea lion population has traditionally been divided into an eastern and western stock at 144° W longitude, roughly through the middle of the Gulf of Alaska. Recent evidence suggests the sea lions in Russia in the Sea of Okhotsk and the Kuril Islands comprise a third Asian stock, while the sea lions on the eastern seaboard of Kamchatka and the Commander Islands belong to the western stock.

In the summer, Steller sea lions tend to shift their range somewhat southward. Thus, though there are no reproductive rookeries in Japan, there are several consistent haulouts around Hokkaidō in the winter and spring.

Steller sea lions are skilled and opportunistic marine predators feeding on a wide range of fish and cephalopod species. Important diet components include walleye pollock, Atka mackerel, halibut, herring, capelin, flatfish Pacific cod, rockfish, sculpins, and cephalopods. They seem to prefer schooling fish and remain primarily in between intertidal zones and continental shelves. They are also known to enter estuarine environments and feed on some semifreshwater fish such as sturgeon. Very occasionally, they have been known to prey on northern fur seals, harbor seals and sea otter pups. They are near the top of the marine food chain, but are susceptible to predation by killer whales and white sharks.