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Marine Ecology Progress Series

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MEPS 552:115-129 (2016)  -  DOI:

Winter distribution and size structure of Antarctic krill Euphausia superba populations in-shore along the West Antarctic Peninsula

Alison C. Cleary1,2,3,*, Edward G. Durbin1, Maria C. Casas1, Meng Zhou4

1Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, USA
2Department of Arctic Biology, University Centre in Svalbard, Longyearbyen, 9171, Norway
3Marine Biological Association of the United Kingdom, Plymouth, PL1 2PB, UK
4Department of Environment, Earth and Ocean Sciences, University of Massachusetts Boston, Boston, Massachusetts 02125, USA
*Corresponding author:

ABSTRACT: Antarctic krill Euphausia superba are a key component of food webs in the maritime West Antarctic Peninsula, and their life history is tied to the seasonal cycles of sea ice and primary production in the region. Previous work has shown a general in-shore migration of krill in winter in this region; however, the very near-shore has not often been sampled as part of these surveys. We investigated distribution, abundance, and size structure of krill in 3 fjordic bays along the peninsula, and in the adjacent Gerlache Strait area using vertically stratified MOCNESS net tows and ADCP acoustic biomass estimates. Krill abundance was high within bays, with net estimated densities exceeding 60 krill m-3, while acoustic estimates were an order of magnitude higher. Krill within bays were larger than krill in the Gerlache Strait. Within bays, krill aggregations were observed near the seafloor during the day with aggregations extending to the sediment interface, and exhibited diel vertical migration higher into the water column at night. We suggest these high winter krill abundances within fjords are indicative of an active seasonal migration by krill in the peninsula region. Potential drivers for such a migration include reduced advective losses and costs, and availability of sediment food resources within fjords. Seasonally near-shore krill may also affect stock and recruitment assessments and may have implications for managing the krill fishery in this area.

KEY WORDS: Euphausiid · Abundance · Diel vertical migration · DVM · WAP · Fjord

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Cite this article as: Cleary AC, Durbin EG, Casas MC, Zhou M (2016) Winter distribution and size structure of Antarctic krill Euphausia superba populations in-shore along the West Antarctic Peninsula. Mar Ecol Prog Ser 552:115-129.

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