Alain Caverivière

Growth of Octopus vulgaris from tagging in Senegalese waters

The growth of Octopus vulgaris (Mollusca: Cephalopoda) in tanks and the sea was modelled and calculated following tagging studies in Senegal. Octopus exhibits a large individual variability in growth and the exponential growth curve is the best fitting theoretical model among other usual models tested. Globally, the growth rates were comparable in the sea and in tanks. Growth rates for the hot season were lower than those for the cold season. Applied to in situ data, the statistical tests showed that females grow more quickly than males. Life expectancy was estimated at between 12 and 14 months. These results question the previous growth curves for the region, all of which were obtained from modal analysis using size or weight–frequencies and were used during stock assessments of this important resource off the north-west African coast.

Observations on the influence of temperature on the length of embryonic development in Octopus vulgaris (Senegal)

Abstract Observations were made in Senegal between 1997–1998 on the length of embryonic development in Octopus vulgaris . The data were from eggs which had been laid by two females in the open sea and fourteen females in concrete tanks. The observations in natural surroundings are the first concerning this species. Hatching occurred after 15–42 d at 27 °C, 29–49 d at 22–23 °C, 57–65 d at 21 °C and 80–87 d at 17 °C. These values are higher than the few data previously recorded in European aquariums, particularly for temperatures under 20 °C.