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  • 1
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    Diving behavior of immature Steller sea lions (Eumetopias jubatus) (2021)
    In:  http://aquaticcommons.org/id/eprint/15147 | 403 | 2014-05-29 07:04:06 | 15147 | United States National Marine Fisheries Service
    Details
    Publication Date: 2021-07-03
    Description: Understanding the ontogenetic relationship between juvenileSteller sea lions (Eumetopias jubatus) and their foraging habitat is key to understanding their relationship toavailable prey and ultimately their survival. We summarize dive and movement data from 13 young-of-the-year (YOY) and 12 yearling Steller sea lions equipped with satellite dive recorders in the Gulf of Alaska and Aleutian Islands (n=18), and Washington (n=7) from 1994 to 2000. A total of 1413 d of transmission (x =56.5 d, range: 14.5–104.1 d) were received. We recorded 222,073 dives, which had a mean depth of 18.4 m (range of means: 5.8−67.9 m; SD=16.4). Alaska YOY dived for shorter periods and at shallower depths (mean depth=7.7 m, mean duration=0.8 min, mean maximum depth=25.7 m, and maximum depth=252 m) than Alaskayearlings (x =16.6 m, 0=1.1 min, x = 63.4 m, 288 m), whereas Washington yearlings dived the longest and deepest (mean depth=39.4 m, mean duration=1.8 min, mean maximumdepth=144.5 m, and maximum depth=328 m). Mean distance for 564 measured trips was 16.6 km; for sea lions ≤10 months of age, trip distance (7.0 km) was significantly less than for those 〉10 months of age (24.6 km). Mean trip duration for 10 of the 25 sea lions was 12.1 h; for sea lions ≤10 months of age, trip duration was 7.5 h and 18.1 h for those 〉10 months of age.We identified three movements types: long-range trips (〉15 km and 〉20 h), short-range trips (〈15 km and 〈20 h) during which the animals left and returned to the same site, and transits to other haul-out sites. Long-range trips started around 9 months of age and occurred most frequently aroundthe assumed time of weaning, whereas short-range trips happened almost daily (0.9 trips/day, n=426 trips). Transitsbegan as early as 7 months of age, occurred more often after 9 months of age, and ranged between 6.5 and 454 km. The change in dive characteristics coincided with the assumed onset of weaning. These yearling sea lion movementpatterns and dive characteristics suggest that immature Steller sea lions are as capable of making the same typesof movements as adults.
    Keywords: Biology ; Fisheries
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 566-582
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  • 2
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    An Accounting of the Sources of Steller Sea Lion, Eumetopias jubatus, Mortality (2021)
    In:  http://aquaticcommons.org/id/eprint/9764 | 403 | 2012-08-16 14:33:10 | 9764 | United States National Marine Fisheries Service
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    Publication Date: 2021-07-09
    Description: During 1991–2000, the west-are additional mortalities that fueled the ern stock of Steller sea lions, Eumetopias decline. We tabulated the levels of reported jubatus, declined at 5.03% (SE = 0.25%) anthropogenic sources of mortality (sub-per year, statistically significant rates (P 〈 sistence, incidental take in fisheries, and 0.10) in all but the eastern Aleutian Islands research), estimated another (illegal shoot-region. The greatest rates of declines oc-ing), then approximated levels of predation curred in the eastern and central Gulf of Alas-(killer whales and sharks). We attempted to ka and the western Aleutian Islands (〉 8.2% partition the various sources of “additional” per year). Using a published correction mortalities as anthropogenic and as addifactor, we estimated the total non-pup pop-tional mortality including some predation. ulation size in Alaska of the western stock We classified 436 anthropogenic mortalities of Steller sea lions to be about 33,000 ani-and 769 anthropogenic plus some predation mals. Based on a published life table and mortalities as “mortality above replace-the current rate of decline, we estimate that ment”; this accounted for 26% and 46% of the total number of mortalities of non-pup the estimated total level of “mortality above Steller sea lions during 1991–2000 was replacement”, respectively. The remaining about 6,383 animals; of those, 4,718 (74%) mortality (74% and 54%, respectively) was are mortalities that would have occurred if not attributed to a specific cause and may be the population were stable, and 1,666 (26%) the result of nutritional stress.
    Keywords: Biology ; Ecology ; Environment ; Management
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 40-45
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  • 3
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    Feeding Ecology of Humpback Whales in Continental Shelf Waters near Cordell Bank, California (2021)
    San Jose State University, Moss Landing Marine Laboratories
    In:  http://aquaticcommons.org/id/eprint/2665 | 29 | 2011-09-29 18:38:49 | 2665
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    Publication Date: 2021-06-26
    Description: Daytime feeding behavior of humpback whales (Megaptera novaeangliae) in Gulf of the Farallones, California, and adjacent waters was observed during autumn of 1988 to 1990. Bodega Canyon, Cordell Bank, and the Farallon Islands were the primary sites of feeding activity. Fecal samples of whales and zooplankton tows contained euphausiids exclusively, dominated by Thysanoessa spinifera (79%), with lesser amounts of Euphausia pacifica (14%), Nyctiphanes simplex (4%), and Nematoscelis difficilis (3%). In 1988 and 1990, whales also were infrequently observed feeding on small schooling fish, presumably Pacific herring (Clupea pallasii), northern anchovy (Engraulis mordax), and juvenile rockfish (Sebastes spp.). Feeding was the most common behavior observed (52%), and less frequently traveling (23%), milling (21 %), and resting (4%). Whales used different methods to consume euphausiid prey at the surface (0-10 m), in shallow water (11-60 m), and deep water (61-140 m). Humpback whales fed at the surface 56% of time in 1988 and 32% of time in 1990, using primarily lateral lunges to capture swarms of euphausiids. In 1989, no surface feeding was observed; however, deep, long-duration dives were followed by extended surface intervals with many respirations. These 1989 observations coincided with increased prey depth as indicated by depth sounder records of diving whales and prey scattering layers. In 1989, increased prey depth and associated feeding behaviors were strongly associated with unusually high surface temperatures, calm seas, and changes in water circulation. Environmental conditions in 1989 triggered the most intense and wide-spread occurrence of red tide in this region since 1980. Red tide samples collected throughout this period contained Alexandrium (=Gonyaulax) catenella and Noctiluca scintillans. Surface feeding was observed only in 1988 and 1990, when surface prey were available and red tides were very limited in extent, duration, and intensity. Annual variations in humpback whale feeding behavior were related to prey availability which is affected by corresponding environmental conditions. (PDF contains 94 pages)
    Description: Masters
    Description: Copyright permission signed by the author is on file with the IAMSLIC archive.
    Keywords: Biology
    Repository Name: AquaDocs
    Type: thesis
    Format: application/pdf
    Format: application/pdf
    Format: 86
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  • 4
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    Neonatal growth of Steller sea lion (Eumetopias jubatus) pups in Alaska (2021)
    In:  http://aquaticcommons.org/id/eprint/9611 | 403 | 2012-08-03 14:34:29 | 9611 | United States National Marine Fisheries Service
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    Publication Date: 2021-07-07
    Description: The growth rate of Steller sea lion (Eumetopias jubatus) pups was studied in southeast Alaska, the Gulf of Alaska, and the Aleutian Islands during the first six weeks after birth. The Steller sea lion population is currently stable in southeast Alaska but is declining in the Aleutian Islands and parts of the Gulf of Alaska. Male pups (22.6 kg [±2.21 SD]) were significantly heavier than female pups (19.6 kg [±1.80 SD]) at 1−5 days of age, but there were no significant differences among rookeries. Male and female pups grew (in mass, standard length, and axillary girth) at the same rate. Body mass and standard length increased at a faster rate for pups in the Aleutian Islands and the western Gulf of Alaska (0.45−0.48 kg/day and 0.47−0.53 cm/day, respectively) than in southeast Alaska (0.23 kg/day and 0.20 cm/day). Additionally, axillary girth increased at a faster rate for pups in the Aleutian Islands (0.59 cm/ day) than for pups in southeast Alaska v(0.25 cm/day). Our results indicate a greater maternal investment in male pups during gestation, but not during early lactation. Although differences in pup growth rate occurred among rookeries, there was no evidence that female sea lions and their pups were nutritionally stressed in the area of population decline
    Keywords: Biology ; Ecology ; Fisheries
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 246-257
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  • 5
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    Distribution and Abundance of Steller Sea Lions, Eumetopias jubatus, on the Asian Coast, 1720's-2005 (2021)
    In:  http://aquaticcommons.org/id/eprint/9715 | 403 | 2012-08-14 16:53:31 | 9715 | United States National Marine Fisheries Service
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    Publication Date: 2021-07-08
    Description: We analyzed published and archived records for the past 250 years to assess changes in distribution and abundance of Steller sea lions, Eumetopias jubatus, along the Asian coast from the Bering Strait to the Korean Peninsula. We found that the northern extent of Steller sea liondistribution has not changed but that the southern limit has moved north by some 500–900 km (~300–500 n.mi.) over the past 50 years. Additionally, the number of animals and their distribution has changed on the Commander Islands, Kuril Islands, and Kamchatka Peninsula. We found no changesin the number of rookeries in the northern Sea of Okhotsk, but a new rookery was established at Tuleny Island on the eastern coast of Sakhalin Island. We estimate that the total abundance of Steller sea lions along the Asian coast in the late 19th century was about 115,000 animals; during the 1960’s, the total estimate was about 27,000 (including pups), most of which were in the Kuril Islands. The fewest number of Steller sea lions occurred in the northwesternPacific in the late 1980’s–early 1990’s when only about 13,000 individuals (including pups) were estimated in the entire region. During the 1990’s, and especially in early2000, an increasing trend in abundance occurred in most areas. Present estimated abundance of Steller sea lions in Asia is about 16,000 individuals (including about 5,000 pups), about half of which occur in the Kuril Islands. Changes in abundance occurred during all time periods but varied by site and period. Specifically, over the past 150 years Steller sea lion abundance at most sites has changed. There were no rookeries on the Commander Islands between1850 and 1960 and abundance was low, but by 1977, abundance increased to 4,800 individuals and a rookery was establishedin the mid 1980’s; abundance there has declined since the early 1980’s and in 2004 only 895 individuals (including 221 pups) were counted during the breeding season. Between 1940 and 2004, abundance along the eastern coast of Kamchatka declined from ~7,000 to ~600 individuals, an overall reduction of 90%. Steller sea lion abundance on the Kuril Islands declined by 〉90% from the 1800’s to 2005; the most severe decline there occurred during 1969–1981. Stellersea lion numbers in the northern part of the Sea of Okhotsk declined during 1930–2002 from 7,200 to 3,100 individuals. Numbers at Tuleny Island have increased since establishmentof a rookery there during 1983–2005 and by immigration from other sites.
    Keywords: Biology ; Conservation ; Ecology ; Fisheries ; Management
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 1-62
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