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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 1 | Copyright

Special issue: Catastrophic reduction of sea ice in the Arctic Ocean...

Biogeosciences, 14, 203-214, 2017
https://doi.org/10.5194/bg-14-203-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 13 Jan 2017

Research article | 13 Jan 2017

Seasonal distribution of short-tailed shearwaters and their prey in the Bering and Chukchi seas

Bungo Nishizawa1, Kohei Matsuno2, Elizabeth A. Labunski3, Kathy J. Kuletz3, Atsushi Yamaguchi1, and Yutaka Watanuki1 Bungo Nishizawa et al.
  • 1Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido, 041-8611, Japan
  • 2Australian Antarctic Division, 203 Channel Highway, Kingston, Tasmania 7050, Australia
  • 3US Fish and Wildlife Service, 1011 E. Tudor Road, Anchorage, AK 99503, USA

Abstract. The short-tailed shearwater (Ardenna tenuirostris) is one of the abundant marine top predators in the Pacific; this seabird spends its non-breeding period in the northern North Pacific during May–October and many visit the southern Chukchi Sea in August–September. We examined potential factors affecting this seasonal pattern of distribution by counting short-tailed shearwaters from boats. Their main prey, krill, was sampled by net tows in the southeastern Bering Sea/Aleutian Islands and in the Bering Strait/southern Chukchi Sea. Short-tailed shearwaters were mainly distributed in the southeastern Bering Sea/Aleutian Islands (60±473birdskm−2) in July 2013, and in the Bering Strait/southern Chukchi Sea (19±91birdskm−2) in September 2012. In the Bering Strait/southern Chukchi Sea, krill size was greater in September 2012 (9.6±5.0mm in total length) than in July 2013 (1.9±1.2mm). Within the Bering Strait/southern Chukchi Sea in September 2012, short-tailed shearwaters occurred more frequently in cells (50 × 50km) where large-sized krill were more abundant. These findings, and information previously collected in other studies, suggest that the seasonal northward movement of short-tailed shearwaters might be associated with the seasonal increase in krill size in the Bering Strait/southern Chukchi Sea. We could not, however, rule out the possibility that large interannual variation in krill abundance might influence the seasonal distribution of shearwaters. This study highlights the importance of krill, which is advected from the Pacific, as an important prey of top predators in the Arctic marine ecosystem.

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To investigate seasonal distribution of short-tailed shearwaters we conducted vessel-based seabird surveys and net samplings of krill, i.e., their main prey, during summer and fall in the Bering Sea and Chukchi Sea. Short-tailed shearwaters in the Bering Sea during summer moved to feed in the Chukchi Sea during fall, which might be associated with the seasonal increase in krill size in the Chukchi Sea.
To investigate seasonal distribution of short-tailed shearwaters we conducted vessel-based...
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