Range‐wide Survey and Estimation of Total Number of Steller Sea Lions in 1989

Loughlin, Thomas R.; Перлов, А. С.; Vladimirov, V.A.

doi:10.1111/j.1748-7692.1992.tb00406.x

Cited by 149 publications

(81 citation statements)

References 4 publications

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“…However, this study represented only a short period within a nearly 30 year decline, during which considerable changes occurred. For example, severe declines first began in the EAI during the early 1970s (Kenyon and Rice 1961, Braham et al 1980, Loughlin et al 1992, but this area is now relatively stable with respect to other regions comprising the western DPS (Fritz and Stinchcomb 2005). Unfortunately, understanding the effects of long-term environmental change on the regulation of population structure has been hampered by lack of historical data on the abundance of Steller sea lions prior to the 1970s (Francis et al 1998), confounding effects of anthropogenic disturbance, three climatic regime shifts (Mantua et al 1997, Mantua andHare 2002), and the idea that proximate causes of mortality have changed during the past three decades (York 1994, York et al 1996, Holmes and York 2003.…”

Section: Chlorophyll a Heterogeneitymentioning

confidence: 99%

Regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions

Lander

Loughlin

Logsdon

et al. 2009

Ecological Applications

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Abstract. Over the past three decades, the decline and altered spatial distribution of the western stock of Steller sea lions (Eumetopias jubatus) in Alaska have been attributed to changes in the distribution or abundance of their prey due to the cumulative effects of fisheries and environmental perturbations. During this period, dietary prey occurrence and diet diversity were related to population decline within metapopulation regions of the western stock of Steller sea lions, suggesting that environmental conditions may be variable among regions. The objective of this study, therefore, was to examine regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions within the context of recent measures of diet diversity and population trajectories. Habitat use was assessed by deploying satellite-depth recorders and satellite relay data loggers on juvenile Steller sea lions (n ¼ 45) over a five-year period (2000)(2001)(2002)(2003)(2004) within four regions of the western stock, including the western, central, and eastern Aleutian Islands, and central Gulf of Alaska. Areas used by sea lions during summer months (June, July, and August) were demarcated using satellite telemetry data and characterized by environmental variables (sea surface temperature [SST] and chlorophyll a [chl a]), which possibly serve as proxies for environmental processes or prey. Spatial patterns of SST diversity and Steller sea lion population trends among regions were fairly consistent with trends reported for diet studies, possibly indicating a link between environmental diversity, prey diversity, and distribution or abundance of Steller sea lions. Overall, maximum spatial heterogeneity coupled with minimal temporal variability of SST appeared to be beneficial for Steller sea lions. In contrast, these patterns were not consistent for chl a, and there appeared to be an ecological threshold. Understanding how Steller sea lions respond to measures of environmental heterogeneity will ultimately be useful for implementing ecosystem management approaches and developing additional conservation strategies.

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Section: Chlorophyll a Heterogeneitymentioning

confidence: 99%

Regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions

Lander

Loughlin

Logsdon

et al. 2009

Ecological Applications

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“…Steller sea lions in the Salish Sea are part of the genetically distinct eastern stock, comprising individuals born at rookeries east and south of Cape Suckling, Alaska at southeastern Alaska, British Columbia, Oregon and California (Bickham et al 1996, Loughlin 1997. That stock has rookeries in southeastern Alaska, British Columbia, Oregon and California (Bigg 1988a, Loughlin et al 1992, RaumSuryan et al 2002, Fisheries and Oceans Canada 2008. California sea lions do not breed north of California, although adults and subadults regularly disperse into Canadian and increasingly Alaskan waters during the nonbreeding season to exploit food resources (Jeffries et al 2000, Maniscalco et al 2004, Carretta et al 2011.…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

California and Steller sea lion use of a major winter haulout in the Salish Sea over 45 years

Edgell¹,

Demarchi²

2012

Mar. Ecol. Prog. Ser.

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Populations of California sea lions Zalophus californianus and Steller sea lions Eumetopias jubatus in much of the eastern North Pacific Ocean have experienced significant growth since being protected in the early 1970s (by the US Marine Mammal Protection Act and Canada's Fisheries Act) from commercial harvests and fisheries-related culls. However, there remains substantial and unexplained variance in the annual number of sea lions using a major winter haulout at the entrance to the Salish Sea. We used linear regression on principal components to show maximum annual sea lion counts, adjusted for population growth, varied as a function of herring biomass and not local sea surface temperatures or precipitation. Results suggest that Race Rocks, British Columbia, Canada, is used as a stopover for an increasing number of sea lions approaching southern Vancouver Island to feed during the nonbreeding season. Reports of resource-driven movements of sea lions are not new, but this is the first study to use a multidecade data set to show resource-driven movements can underlie long-term patterns of population growth. Finally, we found an unexplained change in the seasonal use of Race Rocks affecting both species. Arrival at Race Rocks has occurred in late summer since 1965, but up to 1979 departure had occurred the following spring; since as late as 1997, departure has occurred mid winter. This study highlights the complexities of enacting conservation plans for species with latitudinal distributions and undergoing long-term population change.KEY WORDS: Pacific herring · Race Rocks · Sea surface temperature · Strait of Georgia · Pinniped · Juan de Fuca Strait · Vancouver Island Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 467: [253][254][255][256][257][258][259][260][261][262] 2012 efforts because its position in Juan de Fuca Strait makes it a gateway for thousands of marine mammals and billions of Pacific herring Clupea pallasii and salmon returning to the Salish Sea each year (Bigg 1988a,b, Jeffries et al. 2000 Fig. 1).Seasonal movement of both species of sea lions is influenced in part by the availability of prey fish, as has been documented in Alaska, Washington and California for salmonids, Pacific herring and eulachon Thaleichthys pacificus (Gearin et al. 1986, Lowry et al. 1991, Weise & Harvey 1999, Womble 2005). Scat analyses suggest Pacific herring is one of the most important prey for Steller sea lions in British Columbia, as is Pacific hake Merluccius productus off the coast of Oregon (reviewed in Bredeson et al. 2006). Ano malies in oceanic conditions, such as increased sea surface temperature (SST) or decreased productivity, are shown to correlate with California sea lion distribution and foraging behaviour (Weise et al. 2006, Bargu et al. 2010) and may have played important roles in the decline in the number of Steller sea lions in southern California (Bartho lo mew & Boolootian 1960). Similarly, although we suspect seasonal sea lion distribution...

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“…Only photos of sea lions collected on the one-way trips were The number of sea lions sighted per length of searched subs trip was used as encounter rates for representing the distribution of sea lions in coastal waters as we did not record the distance from the airplane to the sea lions in the water. The encounter rates were calculated only from the data obtained on 3 2001 also could not be used for these calculations due to use of the older global positioning system. The numbers of sea lions in the water collected within 500 m of haulout rocks were also not used to calculate encounter rates.…”

Section: Aerial Survey and Interviewmentioning

confidence: 99%

Distribution of the Steller sea lion Eumetopias jubatus during winter in the northern Sea of Japan, along the west coast of Hokkaido, based on aerial and land sighting surveys

et al. 2006

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Range‐wide Survey and Estimation of Total Number of Steller Sea Lions in 1989

Cited by 149 publications

References 4 publications

Regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions

Regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions

California and Steller sea lion use of a major winter haulout in the Salish Sea over 45 years

Distribution of the Steller sea lion Eumetopias jubatus during winter in the northern Sea of Japan, along the west coast of Hokkaido, based on aerial and land sighting surveys

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