The Role of Predation in the Ecology of the Ringed Seal in Barrow Strait, Northwest Territories, Canada

Hammill, Michael O.; Smith, Thomas G.

doi:10.1111/j.1748-7692.1991.tb00559.x

Cited by 80 publications

(57 citation statements)

References 22 publications

(15 reference statements)

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“…An estimate of the trophic enrichment factor for nitrogen can be obtained by examining isotopic differences between consumers and their diets in cases where such a trophic relationship is well established. Polar bears in the LSR feed almost exclusively on ringed seals Phoca hispida (Stirling & McEwan 1975, Hammill & Smith 1991) and a mean trophic shift of +3.8%0 occurred between muscle tissue of these 2 species. This value also corresponded to the mean dfference between the copepod Calanus hyperboreus and its primary food, POM (Conover & Cota 1985, Head et al 1985 indicating that an isotopic model based on this trophic enrichment factor was possibly apphcable throughout the food web.…”

Section: Resultsmentioning

confidence: 99%

Determination of trophic relationships within a high Arctic marine food web using δ13C and δ15N analysis

Hobson¹,

Welch²

1992

Mar. Ecol. Prog. Ser.

1,099

761

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We measured stable-carbon ( 1 3 C / 1 2~) and/or nitrogen (l5N/l4N) isotope ratios in 322 tissue samples (minus lipids) representing 43 species from primary producers through polar bears Ursus maritimus in the Barrow Strait-Lancaster Sound marine food web during July-August, 1988 to 1990. 613C ranged from -21.6 f 0.3%0 for particulate organic matter (POM) to -15.0 f 0.7%0 for the predatory amphipod Stegocephalus inflatus. 6 1 5~ was least enriched for POM (5.4 +. O.8%0), most enriched for polar bears (21.1 f 0.6%0), and showed a step-wise enrichment with trophic level of +3.8%0. We used this enrichment value to construct a simple isotopic food-web model to establish trophic relationships within thls marine ecosystem. This model confirms a food web consisting primanly of 5 trophic levels. b13C showed no discernible pattern of enrichment after the first 2 trophic levels, an effect that could not be attributed to differential lipid concentrations in food-web components. Although Arctic cod Boreogadus saida is a n important link between primary producers and higher trophic-level vertebrates during late summer, our isotopic model generally predicts closer links between lower trophic-level invertebrates and several species of seabirds and marine mammals than previously established.

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Section: Resultsmentioning

confidence: 99%

Determination of trophic relationships within a high Arctic marine food web using δ13C and δ15N analysis

Hobson¹,

Welch²

1992

Mar. Ecol. Prog. Ser.

1,099

761

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“…Most of our knowledge regarding the polar bear diet is derived from field observations of animals killed by bears (Stirling & McEwan 1975, Hammill & Smith 1991, Derocher et al 2002 or from stomach contents of polar bears (Lønø 1970).…”

Section: Introductionmentioning

confidence: 99%

Fatty acid composition of the adipose tissue of polar bears and of their prey: ringed seals, bearded seals and harp seals

Grahl‐Nielsen¹,

Andersen²,

Derocher³

et al. 2003

Mar. Ecol. Prog. Ser.

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Polar bears Ursus maritimus are predators of phocid seals, but they also forage opportunistically on a variety of other species. In the Barents Sea -Svalbard area, their diet is thought to consist almost exclusively of ringed seals Phoca hispida, bearded seals Erignathus barbatus and harp seals P. groenlandica. When a seal is killed, polar bears preferentially consume the blubber. The fatty acid (FA) compositions of the outer, middle and inner adipose layer of 18 polar bears were compared to each other and also with the FA composition of the blubber of their prey, represented by 10 ringed seals, 10 harp seals and 9 bearded seals. The composition of the FAs in the inner layer of the bear adipose tissue differed from the composition of the outer layer, and was also distinctly different from the composition of the blubber from the prey. Fifteen of the 28 FAs analysed were found in lower relative amounts in the polar bears than in any of the 3 seal species. Eight of the FAs were found in higher relative amounts in polar bears when compared to the 3 prey species. Only 5 of the FAs in polar bears were within the range of relative values found in the prey. This strongly suggests that polar bear adipose tissue has a unique FA composition that is not a straightforward mixture of what they consume, but rather is the result of selective processes prior to and during deposition of lipids in the tissue.

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“…The Barrow Strait floe edge was west of Somerset Island during the winter of 1995/96. This is unusually far west compared to typical years, when it forms from Prince Leopold Island north to Devon Island or from Brodeur Peninsula north to Devon Island (Finley et al 1990, Hammill et al 1991). Belugas may have been able to use these estuaries earlier in 1996 than in most years in the last several decades.…”

Section: DI Is Sc Cu Us Ss Si Io On Nmentioning

confidence: 99%

Surveys of belugas and narwhals in the Canadian High Arctic in 1996

et al. 2002

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S Su ur rv ve ey ys s o of f b be el lu ug ga as s a an nd d n na ar rw wh ha al ls s i in n t th he e C Ca an na ad di ia an n H Hi ig gh h A Ar rc ct ti ic c i in n 1 19 99 96 6 A AB BS ST TR RA AC CT TThe summer range of belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) in Prince Regent Inlet, Barrow Strait and Peel Sound in the Canadian High Arctic was surveyed from 31 July to 3 August 1996 with a visual aerial survey of offshore areas and photographic aerial surveys of concentration areas. The visual survey estimate based on the number of belugas visible to the observers using systematic line transect methods was 10,347 (cv = 0.28). This included corrections for whales that were missed by the observers, observations without distance measurements and an estimate of 1,949 (cv=0.22) belugas from a photographic survey in southern Peel Sound. Using data from belugas tagged with satellite-linked time-depth recorders, the estimate was adjusted for individuals that were diving during the survey which resulted in an estimate of 18,930 belugas (cv = 0.28). Finally, counts of belugas in estuaries, corrected for estuarine surface time, were added to provide a complete estimate of 21,213 belugas (95% CI 10,985 to 32,619). The estimated number of narwhals corrected for sightings that were missed by observers was 16,364 (cv = 0.24). Adjusting this for sightings without distance information and correcting for whales that were submerged produced an estimate of 45,358 narwhals (95% CI 23,397 to 87,932).

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The Role of Predation in the Ecology of the Ringed Seal in Barrow Strait, Northwest Territories, Canada

Cited by 80 publications

References 22 publications

Determination of trophic relationships within a high Arctic marine food web using δ13C and δ15N analysis

Determination of trophic relationships within a high Arctic marine food web using δ13C and δ15N analysis

Fatty acid composition of the adipose tissue of polar bears and of their prey: ringed seals, bearded seals and harp seals

Surveys of belugas and narwhals in the Canadian High Arctic in 1996

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