Seasonal abundance of two important forage species in the North Pacific Ocean, Pacific herring and walleye pollock

Sigler, Michael F.; Csepp, David J.

doi:10.1016/j.fishres.2006.10.007

Cited by 30 publications

(36 citation statements)

References 32 publications

(76 reference statements)

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“…Target (Ona 2003). In addition, Pacific herring acoustic estimates were adjusted for depth compression of the air bladder (Ona 2003) and acoustic shadowing (Zhao & Ona 2003, Sigler & Csepp 2007. Hake and pollock sometimes were found in mixed concentrations; the mixed-species NASC was partitioned to species based on each species' average acoustic backscatter and proportional weight in midwater trawl catches (MacLennan & Simmonds 1992, their Eq.…”

Section: Methodsmentioning

confidence: 99%

“…Data from a year-round study at Lynn Canal (Sigler & Csepp 2007) were added to the Frederick Sound data because the Lynn Canal prey and sea lion abundances varied much more and provided more contrast to detect a numerical response. The numerical response was estimated based on pelagic biomass, but not demersal or nearshore biomass which were indexed (catch rates).…”

Section: Methodsmentioning

confidence: 99%

“…average pelagic fish biomass was 5 × higher than the monthly consumption estimate) and pollock and hake were common (Table 3) year-round. In contrast, herring were concentrated in Lynn Canal only during November to April (Sigler & Csepp 2007) and eulachon were concentrated in Berners Bay only during April and May (Marston et al 2002, Sigler et al 2004. Diet studies imply that the western population of Steller sea lions also follows strong seasonal patterns in consumption of most species of prey (Sinclair & Zeppelin 2002, Sinclair et al 2005.…”

Section: Shifts Among Seasonally Available Preymentioning

confidence: 97%

“…Herring appeared irregularly in satellite bays of Frederick Sound and were abundant in as few as one and as many as 4 bays in a sampling period. In contrast, large, predictable herring schools were present November through February in Lynn Canal (Womble & Sigler 2006, Sigler & Csepp 2007, and their persistence was an important characteristic in determining whether foraging Steller sea lions utilized them (Gende & Sigler 2006).…”

Section: Steller Sea Lion Numerical Responsementioning

confidence: 98%

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Steller sea lion foraging response to seasonal changes in prey availability

Sigler¹,

Tollit²,

Vollenweider³

et al. 2009

Mar. Ecol. Prog. Ser.

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We hypothesized that: (1) Steller sea lion Eumetopias jubatus diet choice is a function of prey availability, (2) sea lions move to take advantage of times and locations of seasonal prey concentrations and (3) the number present depends on the amount of prey available (numerical response). Over 3 yr, typically on a quarterly basis, in Frederick Sound, SE Alaska, multiple measurements were taken of Steller sea lion abundance (aerial surveys), diet (scats), dive behavior (satellite telemetry) and prey availability and caloric density (nearshore, pelagic and demersal fish surveys). We found that Steller sea lions shifted diet composition in response to changes in prey availability of pollock Theragra chalcogramma, hake Merluccius productus, herring Clupea pallasi and salmon Oncorhynchus spp. They selected intermediate-sized fish and avoided small (<10 cm) and large (> 60 cm) fish, and moved between areas as prey became available seasonally. The number of sea lions present depended on the amount of prey available; a standing biomass of 500 to 1700 t of prey in a nonbreeding area such as Frederick Sound, depending on species composition, can attract and sustain about 500 sea lions. Pollock was more frequent in sea lion diet in inside waters of SE Alaska -including Frederick Sound, Stephens Passage and Lynn Canal -than anywhere else in Alaska and contributed ~1⁄ 3 of the dietary energy in Frederick Sound. This finding implies that a diet with substantial year-round contributions from less nutritious, but abundant prey such as pollock can form part of a healthy diet as long as more nutritious prey such as herring, salmon or eulachon Thaleichthys pacificus also are consumed. Our study supports the conclusion that the Steller sea lion is an opportunistic marine predator with a flexible foraging strategy that selects abundant, accessible prey and shifts among seasonally available species.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Shifts Among Seasonally Available Preymentioning

confidence: 97%

Section: Steller Sea Lion Numerical Responsementioning

confidence: 98%

See 2 more Smart Citations

Steller sea lion foraging response to seasonal changes in prey availability

Sigler¹,

Tollit²,

Vollenweider³

et al. 2009

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

show abstract

“…In SEAK, however, SECM and other studies have indicated that salmon growth is not food limited and that stocks interact extensively with little negative impact (Bailey et al 1975;Sturdevant et al 2004Sturdevant et al , 2012. In coastal waters, zooplankton prey fi elds are more likely to be cropped by the more abundant planktivorous forage fi sh, including walleye pollock (Gadus chalcogrammus) and Pacifi c herring (Clupea pallasi) Sigler and Csepp 2007), than by juvenile salmon. These results stress the need to examine the entire epipelagic community in the context of trophic interactions Sturdevant et al 2012) and to compare ecological processes, community structure, and life-history strategies among salmon production areas Orsi et al 2007;Orsi et al 2012bOrsi et al , 2013b.…”

Section: Discussionmentioning

confidence: 99%

Forecasting Pink Salmon Production in Southeast Alaska Using Ecosystem Indicators in Times of Climate Change

Orsi¹,

Fergusson²,

Wertheimer³

et al. 2016

NPAFC Bull.

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Researchers in Alaska have provided accurate pre-season annual forecasts of pink salmon harvest to resource stakeholders of Southeast Alaska (SEAK) in times of climate change. Since 1997, the Southeast Alaska Coastal Monitoring project has collected biophysical data associated with seaward migrating juvenile salmon from May to August, and it has used these data along with larger basin-scale indexes to forecast SEAK pink salmon returns via regression and ecosystem metric models. In nine of the past eleven years (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014), predictions from linear regression models ranged 0-17% of actual harvests, an average absolute forecast deviation of 10%. The primary explanatory variable was juvenile pink salmon peak catch. In some years, models included secondary variables to improve fi t. A supplemental modeling approach was tested recently to better inform stakeholders. This approach incorporated both an annual rank score forecast outlook based on ecosystem metrics, and a visual stoplight color-code graphic. Accurate pre-season salmon forecasts and descriptive outlooks from this applied research has increased economic effi ciency of the fi sh processing industry, enabled managers and resource stakeholders to anticipate harvest with more certainty, helped promote resource sustainability, and provided insight into ecosystem mechanisms related to pink salmon production in a changing climate.

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Mixing it up in Alaska: Habitat use of adult female Steller sea lions reveals a variety of foraging strategies

et al. 2020

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From 2010 to 2015, satellite transmitters were deployed on 16 adult female Steller sea lions (AFSSLs; Eumetopias jubatus) in three regions of Alaska because there is limited information regarding the habitat use of this age class during winter and populations have yet to recover in western Alaska. Two approaches were used to assess how static (distance to shore, sea lion site, and continental shelf break, presence on/off the continental shelf, and bathymetric depth and slope), dynamic (proportion of daylight, fraction of lunar illumination, chlorophyll‐a, wind speed, sea surface height, eddy kinetic energy, and sea surface temperature), and other (region, distinct population segment, and season) covariates affected the habitat use of AFSSLs. Multimodel inference was first used to examine diving behaviors (mean and maximum dive depths, dive frequency) with respect to covariates using linear mixed‐effects models, whereas single model inference was used to examine kernel density estimates (KDEs) of individual monthly utilization distributions (n = 74) in western Alaska with respect to environmental covariates using generalized additive models. Additionally, weighted coefficients from these models were examined for the population as a whole, within each individual, between regions, and across monthly scales. Comparisons of foraging behaviors of AFSSLs over time and space revealed pronounced individual variability within overall broader patterns. Response variables of most models were related to various combinations of predictor variables, but distance to shore was the most influential variable across all models. As expected with a non‐migratory central place forager, frequency of diving and KDEs were greater on the shelf and near shore, though maximum dive depths increased with distance to shore. Interaction effects (proportion of day light*on/off shelf) observed for mean dive depths suggested AFSSLs were feeding on benthic species when in shelf waters near shore, whereas they were likely feeding on vertically migrating prey species while off‐shelf. Relationships regarding diving behaviors and KDEs of AFSSLs relative to dynamic oceanographic variables were not as prominent as those observed for static environmental variables, though some signals were apparent at different scales. Overall, static environmental features likely provided more consistent sources of habitat for prey resources, thereby making them more predictable for AFSSLs.

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Seasonal abundance of two important forage species in the North Pacific Ocean, Pacific herring and walleye pollock

Cited by 30 publications

References 32 publications

Steller sea lion foraging response to seasonal changes in prey availability

Steller sea lion foraging response to seasonal changes in prey availability

Forecasting Pink Salmon Production in Southeast Alaska Using Ecosystem Indicators in Times of Climate Change

Mixing it up in Alaska: Habitat use of adult female Steller sea lions reveals a variety of foraging strategies

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