Seasonal and Spatial Differences in Diet in the Western Stock of Steller Sea Lions (Eumetopias Jubatus)

Sinclair, Elizabeth H.; Zeppelin, Tonya K.

doi:10.1644/1545-1542(2002)083<0973:sasdid>2.0.co;2

Cited by 200 publications

(341 citation statements)

References 17 publications

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“…In the Aleutian Islands, summer diets are dominated by the four species of fish in our sample, especially Atka mackerel (Sinclair and Zeppelin, 2002). The Steller sea lion is an opportunistic carnivore, selecting its prey by availability (Spaulding, 1964).…”

Section: Discussionmentioning

confidence: 99%

Parasites of Forage Fishes in the Vicinity of Steller Sea Lion (Eumetopias Jubatus) Habitat in Alaska

Moles

Heintz

2007

Journal of Wildlife Diseases

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ABSTRACT:Fish serve as intermediate hosts for a number of larval parasites that have the potential of maturing in marine mammals such as Steller sea lions (Eumetopias jubatus). We examined the prevalence of parasites from 229 fish collected between March and July 2002 near two islands used by Steller sea lions in Southeast Alaska and island habitats in the Aleutian Islands. Sea lion populations have remained steady in Southeast Alaska but have been declining over the last 30 yr in the Aleutian Islands. Even though the fish samples near the Southeast Alaska haul-outs were composed of numerous small species of fish and the Aleutian Islands catch was dominated by juveniles of commercially harvested species, the parasite fauna was similar at all locations. Eleven of the 20 parasite taxa identified were in their larval stage in the fish hosts, several of which have been described from mammalian final hosts. Four species of parasite were more prevalent in Southeast Alaska fish samples, and seven parasite species, including several larval forms capable of infecting marine mammals, were more prevalent in fish from the Aleutian Islands. Nevertheless, parasites available to Steller sea lions from common fish prey are not likely to be a major factor in the decline of this marine mammal species.

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Section: Discussionmentioning

confidence: 99%

Parasites of Forage Fishes in the Vicinity of Steller Sea Lion (Eumetopias Jubatus) Habitat in Alaska

Moles

Heintz

2007

Journal of Wildlife Diseases

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“…Critical to the development of such models are data on the diet of Steller sea lions. Diet composition of Steller sea lions is known to vary geographically and seasonally (Sinclair & Zeppelin 2002, Waite & Burkanov 2006). However, due to insufficient data most models have assumed that diet remains constant throughout the year and is similar over broad geographic areas.…”

Section: Introductionmentioning

confidence: 99%

“…Prior to the 1990s, Steller sea lion diets were assessed by examination of stomach contents of shot animals, and just over 400 stomachs were collected from 1945to 1986(Imler & Sarber 1947, Mathisen et al 1962, Thorsteinson & Lensink 1962, Fiscus & Baines 1966, Pitcher 1981, Lowry et al 1982. Considerable effort was made in the 1990s to assess the diet of Steller sea lions in the western range, with the collection of over 3700 scat (fecal) samples throughout the Aleutian Islands and central Gulf of Alaska , Sinclair & Zeppelin 2002. However, individual sitespecific collections were small in number and pooled within 2 broad seasons and across years within datadefined geographical areas.…”

Section: Introductionmentioning

confidence: 99%

“…Despite sampling limitations of historical data, it has been suggested that the diet of Steller sea lions in western Alaska switched from mostly small energyrich schooling fishes (such as herring, capelin, and sand lance) prior to the 1970s, to mostly gadid species (such as walleye pollock) in the Gulf of Alaska and Atka mackerel in the Aleutians in the 1980s and 1990s , Sinclair & Zeppelin 2002. It was also proposed that diet diversity was lowest where the sharpest decline in the Steller sea lion populations occurred , and that diet diversity was a proxy for overall energy content of diet, with low diet diversity equating to low energy content .…”

Section: Introductionmentioning

confidence: 99%

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Spatial and temporal variation in the diet of Steller sea lions in the Kodiak Archipelago, 1999 to 2005

McKenzie¹,

Wynne²

2008

Mar. Ecol. Prog. Ser.

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Spatial and temporal variation in the diet of Steller sea lions Eumetopias jubatus was investigated using scat (fecal) samples collected from 4 regions in the Kodiak Archipelago. Over 2700 scats with identifiable prey were collected from the northern, eastern, southern and western sides of Kodiak Island from 1999 to 2005. Of 76 prey types identified using hard remains, the most important species in terms of frequency of occurrence and numerical abundance were Pacific sand lance Ammodytes hexapterus, walleye pollock Theragra chalcogramma, arrowtooth flounder Atheresthes stomias, Pacific cod Gadus macrocephalus, salmon Oncorhynchus spp., and Pacific herring Clupea pallasi. Significant differences in diet composition were found among regions, seasons, and years, suggesting that the diet of sea lions is strongly influenced by local and temporal distributions and abundances of prey. Herring dominated scat collections from the west coast and accounted for most (14 to 30%) of the differences in regional diet in spring and winter. Annual variation in diet was relatively low in winter, whereas spring and fall diets varied from year to year, with regional-specific shifts in dominant prey. Results from our study generally agree with diet studies conducted in the 1990s, but differ markedly in the relative importance of the major prey species.

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“…Atka mackerel (Pleurogrammus monopterygius) is a major prey species of Steller sea lions (Eumetopias jubatus) in the Aleutian Islands area, as well as an important commercial species targeted by the US groundfish fishery (National Marine Fisheries Service, 1995;Sinclair and Zeppelin, 2002). The listing of the western stock of Steller sea lions as endangered under the Endangered Species Act (ESA; Fritz et al, 1995) in 1990 prompted the need to accurately estimate Atka mackerel abundance on small spatial and temporal scales.…”

Section: Introductionmentioning

confidence: 99%

Estimating movement and abundance of Atka mackerel (Pleurogrammus monopterygius) with tag–release–recapture data

McDermott

Fritz

Haist

2005

Fisheries Oceanography

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A mark-recapture experiment was conducted in Seguam Pass, Alaska, to estimate local Atka mackerel (Pleurogrammus monopterygius) abundance and to evaluate the efficacy of trawl exclusion zones around Steller sea lion (Eumetopias jubatus) rookeries. Atka mackerel were found in dense aggregations near the Aleutian Islands where they are a major prey item of endangered Steller sea lions. In 1999, 1375 tagged fish were released and a biomass of 76 679 metric tonnes (t) was estimated outside a trawl exclusion zone using a simple Petersen model. In 2000, 8773 tagged fish were released and the estimated biomasses were 117 900 t inside and 82 057 t outside the trawl exclusion zones using an integrated tagging model. Movement into the open zone was small after 107 days (0.6%), whereas movement from the open area was potentially large but highly uncertain after 107 days (81%). Our model suggests that trawl exclusion zones in Seguam Pass are effective in separating a large biomass of potential prey for Steller sea lions from the immediate effects of local fisheries. Atka mackerel do not appear to move substantially outside their local aggregations (<70 km), and they show strong habitat preferences within their local home ranges. In one instance, fish released in an area of low Atka mackerel abundance returned to their capture location about 2 miles away. Thus individual Atka mackerel may have an affinity for particular areas within their home range, perhaps resulting from adaptations to local oceanic conditions along the Aleutian Island archipelago.

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Seasonal and Spatial Differences in Diet in the Western Stock of Steller Sea Lions (Eumetopias Jubatus)

Cited by 200 publications

References 17 publications

Parasites of Forage Fishes in the Vicinity of Steller Sea Lion (Eumetopias Jubatus) Habitat in Alaska

Parasites of Forage Fishes in the Vicinity of Steller Sea Lion (Eumetopias Jubatus) Habitat in Alaska

Spatial and temporal variation in the diet of Steller sea lions in the Kodiak Archipelago, 1999 to 2005

Estimating movement and abundance of Atka mackerel (Pleurogrammus monopterygius) with tag–release–recapture data

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