Decline of the Steller Sea Lion in Alaskan Waters

Decline of the Steller Sea Lion in Alaskan Waters PDF

Author: National Research Council

Publisher: National Academies Press

Published: 2003-05-04

Total Pages: 217

ISBN-13: 0309086329

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For an unknown reason, the Steller sea lion population in Alaska has declined by 80% over the past three decades. In 2001, the National Research Council began a study to assess the many hypotheses proposed to explain the sea lion decline including insufficient food due to fishing or the late 1970s climate/regime shift, a disease epidemic, pollution, illegal shooting, subsistence harvest, and predation by killer whales or sharks. The report's analysis indicates that the population decline cannot be explained only by a decreased availability of food; hence other factors, such as predation and illegal shooting, deserve further study. The report recommends a management strategy that could help determine the impact of fisheries on sea lion survival-establishing open and closed fishing areas around sea lion rookeries. This strategy would allow researchers to study sea lions in relatively controlled, contrasting environments. Experimental area closures will help fill some short-term data gaps, but long-term monitoring will be required to understand why sea lions are at a fraction of their former abundance.

Decline of the Steller Sea Lion in Alaskan Waters

Decline of the Steller Sea Lion in Alaskan Waters PDF

Author: National Research Council

Publisher: National Academies Press

Published: 2003-04-04

Total Pages: 216

ISBN-13: 0309168724

DOWNLOAD EBOOK →

For an unknown reason, the Steller sea lion population in Alaska has declined by 80% over the past three decades. In 2001, the National Research Council began a study to assess the many hypotheses proposed to explain the sea lion decline including insufficient food due to fishing or the late 1970s climate/regime shift, a disease epidemic, pollution, illegal shooting, subsistence harvest, and predation by killer whales or sharks. The report's analysis indicates that the population decline cannot be explained only by a decreased availability of food; hence other factors, such as predation and illegal shooting, deserve further study. The report recommends a management strategy that could help determine the impact of fisheries on sea lion survival-establishing open and closed fishing areas around sea lion rookeries. This strategy would allow researchers to study sea lions in relatively controlled, contrasting environments. Experimental area closures will help fill some short-term data gaps, but long-term monitoring will be required to understand why sea lions are at a fraction of their former abundance.

Steller Sea Lion Decline

Steller Sea Lion Decline PDF

Author: Douglas P. DeMaster

Publisher:

Published: 2002

Total Pages: 86

ISBN-13:

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The most likely cause of the moderate decline of western Alaska Steller sea lions, in the 1990s, is poor recruitment (reproduction and survival of young). Also implicated are nutritional stress, predation, and disease. In contrast, nutritional stress alone was the leading hypothesis for a steep decline in sea lions the 1980s. This book has 13 extended abstracts presented at a May 2001 workshop. Attendees included the nation's leading authorities on Alaska's Steller sea lions.

Ethology and Behavioral Ecology of Otariids and the Odobenid

Ethology and Behavioral Ecology of Otariids and the Odobenid PDF

Author: Claudio Campagna

Publisher: Springer

Published: 2022-06-05

Total Pages: 672

ISBN-13: 9783030591861

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This book is focused on the marine mammalian groups the Otariidae and the Odobenidae, otherwise known as fur seals, sea lions and the walrus. In 30 chapters, more than 60 authors from 30 institutions and 13 nationalities, discuss a broad suite of topics from maternal care and mating behavior, through play, cognition and personality, to adaptation to life in the Anthropocene. The authors explore the behaviors that have allowed these semi-aquatic mammals to thrive in the marine realm. Many populations have recovered following historical decimation, with interesting evolutionary consequences which are explored. Detailed, selected, individual species descriptions are also provided, showcasing the behavioral diversity of this engaging, adaptive and highly successful group of marine mammals.

The Steller Sea Lion (Eumetopias Jubatus) Decline and the Gulf of Alaska/Bering Sea Commercial Fishery

The Steller Sea Lion (Eumetopias Jubatus) Decline and the Gulf of Alaska/Bering Sea Commercial Fishery PDF

Author: Daniel Reneau Hennen

Publisher:

Published: 2004

Total Pages: 414

ISBN-13:

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The Steller sea lion (SSL) population in Alaska was listed as threatened under the Endangered Species Act in 1991. Several procedural restrictions were placed on the commercial fisheries of the region at that time in an effort to reduce the potential for human induced mortality on sea lions. Several years have elapsed since these restrictions were put into place and questions about their efficacy abound. In an effort to determine whether or not fisheries interventions have helped the SSL population to recover, estimates of the fishing activity of the Bering Sea/Gulf of Alaska commercial fisheries in the vicinity of individual Steller sea lion rookeries and SSL population trends at those rookeries were made using data from the National Marine Fisheries Service (NMFS) Fisheries Observer Program and Steller Sea Lion Adult Count Database. Fisheries data from 1976-2000 were analyzed in relation to SSL population counts from 1956-2001, at 32 rookeries from the endangered western stock. Linear regression on the principal components of the fisheries data show that a positive correlation exists between several metrics of historical fishing activity and SSL population decline. The relationship is less consistent after 1991, supporting a hypothesis that fishing closures around some of the rookeries have been effective in moderating the localized effects of fishing activity on SSL.

Steller Sea Lions (Eumetopias Jubatus)

Steller Sea Lions (Eumetopias Jubatus) PDF

Author: Andrew W. Trites

Publisher:

Published: 1998

Total Pages: 54

ISBN-13:

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Presents the changes in the Steller sea lion's diet over time (from a diverse diet including fatty fishes to one dominated by pollock), which has resulted in negative reproductive and survival consequences

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