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  • 1
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    Contrasting coastal and shelf nursery habitats of Pacific cod in the southeastern Bering Sea (2015)
    Oxford University Press
    Details
    Publication Date: 2015-01-20
    Description: Shallow, subtidal waters of coastal embayments are the primary nursery habitats of juvenile Pacific cod through much of their range. However, the importance of these habitats to the Bering Sea population is poorly understood as the Bering Sea offers relatively little of this habitat. In this study, we examined the use of demersal and pelagic habitats in the southeast Bering Sea by age-0 Pacific cod. In 4 years of demersal beam trawling on the shelf at depths of 20–146 m, fish were most abundant along the Alaska Peninsula (AKP) at depths to 50 m. In addition, 1 year of spatially intensive beam trawl sampling was conducted at depths of 5–30 m in a nearshore focal area along the central AKP. In this survey, age-0 cod were more abundant along the open coastline than they were in two coastal embayments, counter to patterns observed in the Gulf of Alaska. Demersal sampling in 2012 was conducted synoptically with surveys of surface and subsurface waters over the continental shelf. Age-0 cod were captured in pelagic waters over the middle and outer shelf, with maximum catches occurring over depths of 60–80 m. The similar size distributions of fish in coastal-demersal and shelf-surface habitats and the proximity of concentrations in the two habitat types suggests that habitat use in the Bering Sea occurs along a gradient from coastal to pelagic. While capture efficiencies may differ among trawl types, trawl-based estimates of age-0 cod density in demersal waters along the AKP was 10 times that observed in the highest density pelagic-shelf habitats, demonstrating the importance of coastal nursery habitats in this population. Despite representing a much smaller habitat area, the coastal waters along the AKP appear an important nursery area and support a significant fraction of the age-0 Pacific cod in the Bering Sea.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 2
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    Effects of elevated CO2 levels on eggs and larvae of a North Pacific flatfish (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-27
    Description: The Bering Sea and Gulf of Alaska support a number of commercially important flatfish fisheries. These high latitude ecosystems are predicted to be most immediately impacted by ongoing ocean acidification, but the range of responses by commercial fishery species has yet to be fully explored. In this study, we examined the growth responses of northern rock sole ( Lepidopsetta polyxystra ) eggs and larvae across a range of CO 2 levels (ambient to 1500 µatm) to evaluate the potential sensitivity to ocean acidification. Laboratory-spawned eggs and larvae were reared at 8°C in a flow-through culture system in which CO 2 levels were maintained via computer-controlled injection of CO 2 into a seawater conditioning tank. Overall, we observed only minor effects of elevated CO 2 level on sizes of northern rock sole larvae. Size at hatch differed among offspring from four different females, but there was no significant effect of CO 2 level on egg survival or size at hatch. In three separate larval growth trials, there was little effect of CO 2 level on growth rates through the first 28 d post-hatch (DPH). However, in the one trial extended to 60 DPH, fish reared at the highest CO 2 level had lower condition factors after 28 DPH, suggesting that larvae undergoing metamorphosis may be more sensitive to environmental hypercapnia than earlier pre-flexion stages. These results suggest that while early life stages of northern rock sole are less sensitive to ocean acidification than previously examined flatfish, they may be more sensitive to elevated CO 2 levels than a previously studied gadid with a similar geographic range.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 3
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    Distributional patterns of 0-group Pacific cod (Gadus macrocephalus) in the eastern Bering Sea under variable recruitment and thermal conditions (2012)
    Oxford University Press
    Details
    Publication Date: 2012-02-17
    Description: Hurst, T. P., Moss, J. H., and Miller, J. A. 2012. Distributional patterns of 0-group Pacific cod ( Gadus macrocephalus ) in the eastern Bering Sea under variable recruitment and thermal conditions. – ICES Journal of Marine Science, 69: 163–174. Despite the importance of Pacific cod in Bering Sea fisheries and foodwebs, little is known about the habitat use and the distribution of early life stages. We analysed 6 years of catch data for 0-group Pacific cod in fishery-independent surveys of the Bering Sea shelf. Juvenile cod were most commonly captured on the middle shelf over depths of 50–80 m and were rarely captured north of 58°N. Consistently high catches were observed east of the Pribilof Islands and north of Port Moller along the Alaska Peninsula. There was evidence of density-dependent habitat selection at the local scale as the frequency of occurrence increased with regional catch per unit effort. At the basin scale, the southerly distribution of the weak 2009 cohort suggested the possibility of a range contraction for small cohorts. There was no consistent shift in the distribution of juvenile Pacific cod in response to interannual climate variability. These results for Pacific cod contrast with those observed for walleye pollock, which appears to exhibit greater variance in distribution, but are similar to patterns observed for juvenile Atlantic cod. Future work should focus on distribution in nearshore habitats and examine the patterns of dispersal and the connectivity of the Bering Sea and Gulf of Alaska populations.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 4
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    Effects of ocean acidification on hatch size and larval growth of walleye pollock (Theragra chalcogramma) (2013)
    Oxford University Press
    Details
    Publication Date: 2013-06-29
    Description: Hurst, T. P., Fernandez, E. R., and Mathis, J. T. 2013. Effects of ocean acidification on hatch size and larval growth of walleye pollock ( Theragra chalcogramma ). – ICES Journal of Marine Science, 70: 812–822. Rising atmospheric concentrations of CO 2 are predicted to decrease the pH of high-latitude oceans by 0.3–0.5 units by 2100. Because of their limited capacity for ion exchange, embryos and larvae of marine fishes are predicted to be more sensitive to elevated CO 2 than juveniles and adults. Eggs and larvae of walleye pollock ( Theragra chalcogramma ) were incubated across a broad range of CO 2 levels (280–2100 µatm) to evaluate sensitivity in this critical resource species. Slightly elevated CO 2 levels (~450 µatm) resulted in earlier hatching times, but differences among egg batches were greater than those observed across CO 2 treatments. Egg batches differed significantly in size-at-hatch metrics, but we observed no consistent effect of CO 2 level. In three independent experiments, walleye pollock were reared at ambient and elevated CO 2 levels through the early larval stage (to ~30 days post-hatch). Across trials, there were only minor effects of CO 2 level on size and growth rate, but fish in the ambient treatments tended to be slightly smaller than fish reared at elevated CO 2 levels. These results suggest that growth potential of early life stages of walleye pollock is resilient with respect to the direct physiological effects of ocean acidification.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 5
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    Contrasting coastal and shelf nursery habitats of Pacific cod in the southeastern Bering Sea (2014)
    Oxford University Press
    Details
    Publication Date: 2014-08-26
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press on behalf of International Council for the Exploration of the Sea.
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  • 6
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    Effects of ocean acidification on hatch size and larval growth of walleye pollock (Theragra chalcogramma) (2013)
    Oxford University Press
    Details
    Publication Date: 2013-07-01
    Description: Hurst, T. P., Fernandez, E. R., and Mathis, J. T. 2013. Effects of ocean acidification on hatch size and larval growth of walleye pollock (Theragra chalcogramma). – ICES Journal of Marine Science, 70: 812–822. Rising atmospheric concentrations of CO2 are predicted to decrease the pH of high-latitude oceans by 0.3–0.5 units by 2100. Because of their limited capacity for ion exchange, embryos and larvae of marine fishes are predicted to be more sensitive to elevated CO2 than juveniles and adults. Eggs and larvae of walleye pollock (Theragra chalcogramma) were incubated across a broad range of CO2 levels (280–2100 µatm) to evaluate sensitivity in this critical resource species. Slightly elevated CO2 levels (∼450 µatm) resulted in earlier hatching times, but differences among egg batches were greater than those observed across CO2 treatments. Egg batches differed significantly in size-at-hatch metrics, but we observed no consistent effect of CO2 level. In three independent experiments, walleye pollock were reared at ambient and elevated CO2 levels through the early larval stage (to ∼30 days post-hatch). Across trials, there were only minor effects of CO2 level on size and growth rate, but fish in the ambient treatments tended to be slightly smaller than fish reared at elevated CO2 levels. These results suggest that growth potential of early life stages of walleye pollock is resilient with respect to the direct physiological effects of ocean acidification.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press on behalf of International Council for the Exploration of the Sea.
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  • 7
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    Effects of elevated CO2levels on eggs and larvae of a North Pacific flatfish (2015)
    Oxford University Press
    Details
    Publication Date: 2015-04-06
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press on behalf of International Council for the Exploration of the Sea.
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  • 8
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    Distributional patterns of 0-group Pacific cod (Gadus macrocephalus) in the eastern Bering Sea under variable recruitment and thermal conditions (2012)
    Oxford University Press
    Details
    Publication Date: 2012-03-01
    Description: Hurst, T. P., Moss, J. H., and Miller, J. A. 2012. Distributional patterns of 0-group Pacific cod (Gadus macrocephalus) in the eastern Bering Sea under variable recruitment and thermal conditions. – ICES Journal of Marine Science, 69: 163–174. Despite the importance of Pacific cod in Bering Sea fisheries and foodwebs, little is known about the habitat use and the distribution of early life stages. We analysed 6 years of catch data for 0-group Pacific cod in fishery-independent surveys of the Bering Sea shelf. Juvenile cod were most commonly captured on the middle shelf over depths of 50–80 m and were rarely captured north of 58°N. Consistently high catches were observed east of the Pribilof Islands and north of Port Moller along the Alaska Peninsula. There was evidence of density-dependent habitat selection at the local scale as the frequency of occurrence increased with regional catch per unit effort. At the basin scale, the southerly distribution of the weak 2009 cohort suggested the possibility of a range contraction for small cohorts. There was no consistent shift in the distribution of juvenile Pacific cod in response to interannual climate variability. These results for Pacific cod contrast with those observed for walleye pollock, which appears to exhibit greater variance in distribution, but are similar to patterns observed for juvenile Atlantic cod. Future work should focus on distribution in nearshore habitats and examine the patterns of dispersal and the connectivity of the Bering Sea and Gulf of Alaska populations.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press on behalf of International Council for the Exploration of the Sea.
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