Steller Sea Lion (Eumetopias Jubatus)
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Appendices
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status
- Summary of Status Report
- Technical Summary
- Acknowledgements and Literature Cited
- Biographical Summaries of the Report Writers, Authorities Consulted, and Collections Examined
The terrestrial sites used by Steller sea lions In British Columbia generally fall into three distinct categories: 1) rookeries where animals congregate during May-August to give birth, mate, and nurse pups; 2) year-round haulouts that are usually occupied continuously; and 3) winter haulout sites that are used less regularly and primarily during the non-breeding season (Bigg 1985). Rookeries generally have peripheral haulout sites associated with them that are occupied mainly by non-breeding males and juveniles. In most cases animals continue to use rookeries as haulout sites throughout the year, albeit in much reduced numbers.
Steller sea lions are extremely traditional in the sites they use to give birth and mate. Studies of marked individuals indicate that females tend to return to their rookeries of birth, and will return faithfully to a single rookery each year (Raum-Suryan et al. 2002). The three breeding areas currently used in BC all appear to have been well established at the turn of the century when the first sea lion survey was conducted (Newcombe and Newcombe 1914), and have been used continuously despite the disturbances caused by predator control programs and commercial harvests (Pike and Maxwell 1958; Bigg 1985; Olesiuk 2003). No new rookeries have been colonized in BC, or for that matter throughout other parts of their North Pacific range, with the exception of Southeast Alaska and Gulf of Alaska where some haulouts became rookeries.
Updated from Bigg (1985) based on Olesiuk (2003).
One of the most striking features of rookeries is their remoteness and generally the absence of terrestrial predators such as wolves and bears. Steller sea lions propagate on some of the most isolated, barren outcroppings in the North Pacific Ocean. They appear to be located in regions that have relatively high currents, high salinity, low surface temperatures and shallow waters--which presumably reflects high ocean productivity and hence optimum feeding areas (Ban et al., unpublished data). Essential haulout features seem to be relatively flat terrain, accessibility, and protection from swell and waves (Edie 1977). Sea lions use protected areas during storms and wet areas during extremely hot weather (Edie 1977). Access to high ground is also important for whelping, although older animals capable of going to sea will use lower and more exposed areas. The rookeries in BC are comprised of rocky ledges, except in recent years when increasing numbers of animals began breeding on the gravel beaches along the eastern (leeward) side of Triangle Island (Olesiuk, unpublished data).
The 21 year-round haulout sites in BC are generally situated in exposed areas along the outer coast, and are comprised of rocky islets and ledges. Approximately half of them were noted during the first surveys in 1913 (Newcombe and Newcombe 1914), while about one-quarter appear to have been colonized since aerial surveys were initiated in the early 1970s. As populations have increased in BC, many some sites formerly used mainly during winter (see below) have been occupied more continuously, and have been re-classified as year-round haulouts (Olesiuk 2003).
Use of winter haulouts appears to be more fluid than year-round sites. Most winter haulouts are situated in protected areas, such as the Strait of Georgia, Strait of Juan de Fuca and Queen Charlotte Strait. In addition to natural substrates, wintering haulouts include logbooms, floats, jetties and docks. Animals can also rest in the water during storms or heavy swells when haulouts are awash, or when they are near concentrations of prey without suitable nearby haulouts (Kenyon and Rice 1961). This behaviour often occurs in groups and is referred to as rafting. Animals typically lie at the surface with their flippers extended into the air, with their snouts occasionally breaking the surface as the animals breathe (Olesiuk and Bigg 1988). In the southern part of BC, winter haulouts are often shared with adult- and subadult-male California sea lions (Zalophus californianus) (Hancock 1970; Brenton 1977; Bigg 1985).
Our understanding of how Steller sea lions use their aquatic habitat is poor. Animals are generally observed within 60 km of land and in water depths less than 400 m, but may venture several hundred kilometers offshore and occur off the continental shelf (Kenyon and Rice 1961; Merrick and Loughlin 1997). Steller sea lions also occasionally venture into freshwater (Jameson and Kenyon 1977; Roffe and Mate 1984; Beach et al. 1985). In BC, sea lions often congregate in the lower Fraser River during the spring eulachon run(Bigg 1985), and are occasionally seen rafting as far as 35 km upriver (Olesiuk, unpublished data). Steller sea lions also congregate in estuaries during autumn to feed on pre-spawning salmon (Bigg et al. 1990).
The first rookery abandoned following the culls of 1913-1915 may have been Watch Rock where a dozen pups were counted in 1913 (Bigg 1985). By 1938, control programs had extirpated the two other rookeries that formed the Sea Otter Group--Virgin Rocks and Pearl Rocks (Fig. 2). Few predator control kills were conducted in the following decade. However, substantial kills were made by the Canadian air force and navy in the 1940s during practice bombings on the remaining breeding populations (Pike and Maxwell 1958; Bigg 1985). Predator control and commercial harvesting resumed during 1956-66 and further reduced the BC population (Bigg 1985; Olesiuk 2003). No further attempts have been made to eradicate Steller sea lions since they were protected in 1970 under the Fisheries Act. Pupping has not resumed at the eradicated rookeries since culling stopped, and no new rookeries have been established in BC since the first census was made in the early 1900s.
The range of the Steller sea lion crosses the international boundaries with the United States. Breeding populations occur in California and Oregon, but not in Washington State. In Southeast Alaska, no rookeries were known to occur during the early part of the 1900s. However, animals began breeding at Forrester Island, situated about 25 km north of the BC-Alaska border, shortly after control programs were initiated in BC. Rowley(1929) mentioned, without giving a date, that a rookery existed there in the late 1920s with 50-100 animals, and Imler and Sarber (1947) reported a count of 350 in August 1945. The Forrester Island rookery increased dramatically, with 2500 animals present by 1957 (Mathisen and Lopp 1963), and now constitutes the largest breeding aggregation in the world. Given the close proximity of this rookery to the BC border, it is difficult to separate BC from SE Alaska when assessing population trends. Steller sea lions also established new rookeries in Southeast Alaska at the Hazy Islands in about 1985 and White Sisters Island in 1992, and more recently have begun pupping at Graves and Baili Rocks (Calkins et al. 1999; Pitcher et al. 2003).
Management of marine mammals in Canadian waters is a federal responsibility. Since 1970, Steller sea lions have been protected by various regulations enacted under the Fisheries Act and enforced by the Department of Fisheries and Oceans (DFO). Although fish habitat--including by definition sea lion habitat--is generally protected under the Fisheries Act, the breeding rookeries at the Scott Islands, as well as several haulout sites within this archipelago, have also been designated as Ecological Reserves under the BC Ecological Reserves Act. The rookery at Cape St. James was also once an Ecological Reserve, but became part of Gwaii Haanas National Park Reserve when it was created in 1987 under the federal National Parks Act. The Gwaii Haanas Park Reserve is co-managed by the federal government and the Haida Nation, and legislation was recently passed that will formally allow the creation of a marine component to the reserve. Thus 2 of the 3 existing breeding areas are protected (only Danger Rocks is not). Extraction of resources is not permitted, and visitation is restricted through the issuance of permits. DFO also recently began establishing a series of Marine Protected Areas (MPA) under the new Oceans Act introduced in 1996. One of the first two pilot MPAs to be established on the Pacific coast of Canada was Race Rocks, in part because it was recognized as an important winter haulout for Steller and California sea lions.
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