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Krill demography and large-scale distribution in the Western Indian Ocean sector of the Southern Ocean (CCAMLR Division 58.4.2) in Austral summer of 2006

Citation

Kawaguchi, S and Nicol, S and Virtue, P and Davenport, SR and Casper, R and Swadling, KM and Hosie, GW, Krill demography and large-scale distribution in the Western Indian Ocean sector of the Southern Ocean (CCAMLR Division 58.4.2) in Austral summer of 2006 , Deep-Sea Research. Part II: Topical Studies in Oceanography, 57, (9-10) pp. 934-947. ISSN 0967-0645 (2010) [Refereed Article]

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DOI: doi:10.1016/j.dsr2.2008.06.014

Abstract

Krill demography was studied during a large-scale survey of the South Western Indian sector of the Southern Ocean conducted in late January to late February 2006 (BROKE-West). The survey progressed from 30oE in late January to 80oE in late February and was bounded in the North by 62S. The average krill density calculated from the catches of the RMT 8 net for four geographical strata ranged from 0.84-68 individuals per 1000 m-3, with overall mean of 6.7 individuals per 1000 m-3. Krill distribution and its population structure were analysed using cluster and mixture analysis of the length frequency distribution, showing small sized krill (modal size of 25-30 mm) broadly distributed in the centre of the western area whereas middle and large sized krill (modal size of 35-45 mm and 45-55 mm, respectively) mainly distributed in the middle and eastern half of the survey area. These findings are discussed in the context of the observed geographic and oceanographic structures; the continental slope area, fronts, currents and gyres. Proportional recruitment indices ranged 0.089-0.226 for R1 (age 1+ recruitment) and 0.204-0.440 for R2 (age 2+ recruitment) in the four strata. Recruitment analysis revealed differences between western and eastern halves of the surveyed area, suggesting the possible existence of separate self-sustaining populations linked to the Weddell Gyre and Prydz Bay Gyre systems. Krill larvae were mainly observed along the shelf break, implying the early onset of spawning in mid-November. The series of coastal polynyas developing in the early spring may be one of the important habitats allowing use of early season phytoplankton growth for early maturation and spawning, and those larvae would be transported westwards by the coastal current along the shelf slope.

Item Details

Item Type:Refereed Article
Keywords:Antarctic krill; Recruitment; Density; Distribution; Sexual maturity; Southern Ocean, Indian Ocean sector (30E to 80E)
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and Estuarine Ecology (incl. Marine Ichthyology)
Objective Division:Environment
Objective Group:Flora, Fauna and Biodiversity
Objective Field:Antarctic and Sub-Antarctic Flora, Fauna and Biodiversity
Author:Virtue, P (Associate Professor Patti Virtue)
Author:Casper, R (Dr Ruth Casper)
Author:Swadling, KM (Dr Kerrie Swadling)
ID Code:61070
Year Published:2010
Web of Science® Times Cited:17
Deposited By:TAFI - Marine Research Laboratory
Deposited On:2010-02-25
Last Modified:2011-03-22
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