The decline of Steller sea lions Eumetopias jubatus in Alaska : a review of the nutritional stress hypothesis

@article{Trites2003TheDO,
  title={The decline of Steller sea lions Eumetopias jubatus in Alaska : a review of the nutritional stress hypothesis},
  author={Andrew W. Trites and Carolyn Patricia Donnelly},
  journal={Mammal Review},
  year={2003},
  volume={33},
  pages={3-28}
}
The decline of Steller sea lions Eumetopias jubatus in the Gulf of Alaska and Aleutian Islands between the late 1970s and 1990s may have been related to reduced availability of suitable prey. Many studies have shown that pinnipeds and other mammals suffering from nutritional stress typically exhibit reduced body size, reduced productivity, high mortality of pups and juveniles, altered blood chemistry and specific behavioural modifications. 2. Morphometric measurements of Steller sea lions… 

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References

SHOWING 1-10 OF 137 REFERENCES
REDUCED BODY SIZE OF FEMALE STELLER SEA LIONS FROM A DECLINING POPULATION IN THE GULF OF ALASKA
TLDR
Body growth of female Steller sea lions collected in the Gulf of Alaska during two time periods, 1975–1978 just prior to or early in the decline and 1985–1986 when the decline was well established, found that growth was reduced during the 1980s, supporting the undernutrition hypothesis.
Prey consumption of Steller sea lions (Eumetopias jubatus) off Alaska: How much prey do they require?
TLDR
Estimated requirements were highest in regions where Steller sea lions consumed higher proportions of low–energy-density prey and experienced the highest rates of population decline and experiencedThe highest ratesof population decline.
WINTER ECOLOGY OF STELLER SEA LIONS (Eumetopias jubatus) IN ALASKA
TLDR
Mothers suckle male offspring more than female offspring, and spend less time on shore to provide for the higher metabolic needs of males, and Mothers with yearlings have higher demands than those with pups and should spend more time nursing and more time at sea foraging.
Maternal attendance patterns of Steller sea lions (Eumetopias jubatus) from stable and declining populations in Alaska
TLDR
For both populations, the mean time that mothers foraged increased as pups grew older, whereas the time that they spent on shore with their pups became shorter, counter to initial predictions.
Behaviour of lactating stellar sea lions (eumetopias jubatus) during breeding season : a comparison between a declining and stable population in Alaska
Female attendance patterns and activity budgets of Alaskan Steller sea lions (Eumetopias jubatus) were compared at two sites using scan sampling over two summer breeding seasons in 1994 and 1995 at
A comparison of Steller sea lion, Eumetopias jubatus, pup masses between rookeries with increasing and decreasing populations
TLDR
Although numbers of pups observed dead on the rookeries have been consistently low during and immediately after the pupping season (NMFSl), it is difficult to measure early survival of Steller sea lion pups because carcasses rapidly disappear from rookeries (due to storms, tides, and scavengers).
Changes in the abundance of Steller sea lions (Eumetopias jubatus) in Alaska from 1956 to 1992: how many were there?
The size of Steller sea lion populations in the Gulf of Alaska and Aleutian Islands was estimated by applying life table statistics to counts of pups and adults (non-pups) at rookery sites. Total
Pollock and the decline of Steller sea lions: testing the junk-food hypothesis.
TLDR
Results from the captive-feeding studies are consistent with the junk-food hypothesis and have serious implications for Steller sea lions that have been eating primarily pollock in the Gulf of Alaska and the Aleutian Islands.
Health status of young Alaska Steller sea lion pups (Eumetopias jubatus) as indicated by blood chemistry and hematology.
TLDR
Blood chemistry and hematology data showed no indication that Steller sea lion pups <1 month old from areas of population decline were nutritionally compromised and exhibited typical mammalian relationships.
DECLINE IN ABUNDANCE OF THE NORTHERN SEA LION, EUMETOPIAS JUBATUS, IN ALASKA, 1956·86
Aerial, ship, and onshore surveys were conducted to assess the abundance of northern sea lions, Eum~tQpias juba.tlls, in southwestern Alaska. from the central Gulf of Alaska through the central Aleu­
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