Monday, January 30, 2006

Steller Sea Lions in the Icy Strait

Steller Sea Lions on an Inian Islands Pull-out in the Icy Strait near Glacier Bay National Park in Alaska.

Some information about the Stellar Sea Lions:

The Steller sea lion (Eumetopias jubatus) is the largest member of the Otariid (eared seal) family. Males may be up to 325 cm (10-11 ft) in length and can weigh up to 1,100 kg (2,400 lb). Females are smaller than males, 240-290 cm (7.5-9.5 ft) in length and up to 350 kg (770 lb) in mass. Males and females are light buff to reddish brown and slightly darker on the chest and abdomen; naked parts of the skin are black. Wet animals usually appear darker than dry ones. Pups are about 1 m (3.3 ft) in length and 16-23 kg (35-50 lb) at birth and grow to about 30-40 kg (65-90 lb) after 6-10 weeks. Pups are dark brown to black until 4 to 6 months old when they molt to a lighter brown. By the end of their second year, pups have taken on the same pelage color as adults.

Bulls become mature between 3 and 8 years of age, but typically are not massive enough to hold territory successfully until 9 or 10 years old. Females reproduce for the first time at 4 to 6 years of age, bearing at most a single pup each year. Pups are born from late May through early July, with peak numbers of births during the second or third week of June. Females stay with their pups for about 9 days before beginning a regular routine of foraging trips to sea. Females mate 11 to 14 days after giving birth. Implantation takes place in late September or early October, after a 3-4 month delay. Weaning is not sharply defined as it is for most other pinniped species, but probably takes place gradually during the winter and spring prior to the following breeding season. It is not uncommon to observe 1- or 2-year-old sea lions suckling from an adult female.

Steller sea lion are distributed across the North Pacific Ocean rim from northern Hokkaido, Japan, through the Kuril Islands, Okhotsk Sea, and Commander Islands in Russia, the Aleutian Islands, central Bering Sea, and southern coast of Alaska, and south to the Channel Islands off California. During the May-to-July breeding season, Steller sea lions congregate at more that 40 rookeries, where adult males defend territories, pups are born, and mating takes place. Non-reproductive animals congregate to rest at more than 200 haul-out sites where little or no breeding takes place. Sea lions continue to gather at both rookeries and haul-out sites outside of the breeding season.

Steller sea lions are opportunistic predators, feeding primarily of a wide variety of fishes and cephalopods. Prey varies geographically and seasonally. Some of the more important prey species in Alaska include walleye pollock (Theragra chalcogramma), Atka mackerel (Pleurogrammus monopterygius), Pacific herring (Clupea harengus), Capelin (Mallotus villosus), Pacific sand lance (Ammodytes hexapterus), Pacific cod (Gadus macrocephalus), and salmon (Oncorhynchus spp.). Steller sea lions have been known to prey on harbor seal, fur seal, ringed seal, and possibly sea otter pups, but this would represent only a supplemental component to the diet.

Information about the Icy Stait:

Glacier Bay is the principal tributary to Icy Strait-Cross Sound, a large passage that links the northern waters of the Alexander Archipelago to the open sea. Secondary inlets join this waterway from the north and south. At its western margin, Cross Sound broadens out into a complex of small fjords and offshore islets that face the open sea.

Icy Strait - Cross Sound and its complex of tributary inlets provide a wide array of open waters and sheltered estuaries with an equally wide array of water depths and bottom types. Consequently the area hosts important concentrations of a variety of marine species, notably halibut, salmon and Tanner crab, humpback whales, harbor porpoises and marbled murrelets. The recently reintroduced sea otter is thriving. Being along the northern terminus of sheltered waterways extending almost unbroken to Seattle, this waterway is a major conduit for animal movements into and out of southeast Alaska waters, as it is for transient vessel traffic as well. These waters have been major commercial fishing grounds for over a century. Sightseeing, sport fishing and ecotourism are rapidly increasing activities.

Mainland portions of the province west of Glacier Bay are at present dominated by the Brady Glacier. Unlike Glacier Bay ice, the Brady is near its Little Ice Age limits, directly covering much land with ice, and indirectly influencing many valleys and inlets around its periphery with outwash and melt water. Other lands in the province have, with minor exception, been uninfluenced by ice for 13,000 years. A rich array of mature plant communities have developed on these older lands, including major tracts of luxuriant old-growth forest that host substantial deer and brown bear populations. Mainland plant communities, though generally younger, are far richer in mammal species, due to the difficulty of crossing the water barrier posed by Icy Strait.

Most of the mainland is in Glacier Bay National Park and Preserve. Most lands to the south, along with islands in Icy Strait and a strip along the Park's eastern margin, are included within the Tongass National Forest. Private lands are extensive around Hoonah and to a lesser degree along Excursion Inlet. Logging is prohibited on protected National Forest lands in the western half and eastern extremity of this province. Nearly every other valley of the remainder of the National Forest has been roaded and logged to some degree. Native corporation lands have been very heavily logged.

The largely Tlingit community of Hoonah, with a population of about 1,000, has traditionally been based on fishing and subsistence gathering. During the last two decades, however, timber harvesting has provided an additional sector to its economy. Primarily during summer, a few hundred people reside along Excursion Inlet. Many of these seasonal residents work at the large fish processing facility. Elfin Cove is a fishing and tourism community of less than 100 people on the southeast margin of Cross Sound.