Journal Article

Seasonal population dynamics of <i>Octopus vulgaris</i> in the eastern Mediterranean

Stelios Katsanevakis and George Verriopoulos

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 63, issue 1, pages 151-160
Published in print January 2006 | ISSN: 1054-3139
Published online January 2006 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2005.07.004
Seasonal population dynamics of Octopus vulgaris in the eastern Mediterranean

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The population density of Octopus vulgaris was measured by visual census with scuba diving in coastal areas in Greece (eastern Mediterranean). A time-variant, stage-classified, matrix population model was developed to interpret the seasonal variation of octopus stage densities and to estimate several life cycle parameters. An annual and a semi-annual periodic cycle were found in the stage densities. A main peak of benthic settlement was observed during summer and a secondary, irregular one during late autumn. Two spawning peaks were estimated, a main one during late winter–spring and a secondary one during late summer–early autumn. More than 50% of the just-settled individuals will eventually die after 3 months. Mortality rate declines, as individuals grow larger, reaches a minimum approximately 6 months after settlement, and then grows again probably because of terminal spawning. The life expectancy of recently settled individuals (<50 g) during their summer peak is approximately 5 months. The lifespan of the common octopus is estimated to be between 12 and 15 months. The octopuses' mean specific growth rates (±s.d.) in their natural environment were 1.61 ± 0.30 d−1 for 50–200 g individuals and 1.19 ± 0.31 d−1 for 200–500 g individuals.

Keywords: abundance; cephalopod; growth; matrix population model; mortality; octopus; population dynamics; seasonal variation; settlement; spawning

Journal Article.  4930 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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