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Marine Ecology Progress Series

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MEPS 345:199-210 (2007)  -  DOI:

Male krill grow fast and die young

So Kawaguchi1,*, Luke A. Finley1,2, Simon Jarman1, Steven G. Candy1, Robin M. Ross3, Langdon B. Quetin3, Volker Siegel4, Wayne Trivelpiece5, Mikio Naganobu6, Stephen Nicol1

1Australian Antarctic Division, Department of the Environment and Water Resources, 203 Channel Highway, Kingston, Tasmania 7050, Australia
2Department of Zoology, The University of Melbourne, Victoria 3010, Australia
3Marine Science Institute, University of California at Santa Barbara, Santa Barbara, California 93106-6150, USA
4Seafisheries Research Institute, Palmaille 9, 22767 Hamburg, Germany
5US AMLR Program, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, California 92037, USA
6National Research Institute of Far Seas Fisheries, 2-12-4, Fukuura, Kanazawa-ku, Yokohama, Kanagawa 236-8648, Japan

ABSTRACT: The size-differentiated sex ratio (proportion of males, PM) of Antarctic krill Euphausia superba was examined with an extensive dataset derived from scientific surveys in the Indian Ocean sector and the southwest Atlantic sector, and from the krill fishery in the Southern Ocean. The percentage of males in size classes of adult krill was generally high in krill of 30 to 35 mm total length, always low in 38 to 42 mm krill, sometimes showed higher values in 45 to 50 mm krill, but always decreased in the largest krill (>50 mm). This pattern was reproduced by a model simulation that assumed faster growth and a shorter lifespan for males when compared to females. These results suggest that the numbers of males should decline with time unless new recruits enter the population. Indeed, interannual variations in PM from the field (net collected data and penguin diet data) showed a decline in the proportion of males when several years of low recruitment followed a recruitment pulse. These results lead us to conclude that male krill grow faster and have a shorter lifespan than females in the natural environment.

KEY WORDS: Euphausia superba · Sex ratio · Proportion of males · Lifespan · Mortality · Longevity · Recruitment · Length-frequency distribution

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Cite this article as: Kawaguchi S, Finley LA, Jarman S, Candy SG and others (2007) Male krill grow fast and die young. Mar Ecol Prog Ser 345:199-210.

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