Journal of the Marine Biological Association of the UK



Research Article

Population biology of Octopus vulgaris on the temperate south-eastern coast of South Africa


A.  Oosthuizen a1c1 and M.J.  Smale a2
a1 Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown, 6140, South Africa
a2 Port Elizabeth Museum, PO Box 13147, Humewood, Port Elizabeth, 6013, South Africa

Abstract

Population structure and biology of Octopus vulgaris was investigated along the south-eastern coast of South Africa. Samples were collected inter- and sub-tidally as a precursor to the establishment of an experimental octopus fishery in the region. In total, 300 (intertidal) and 147 (subtidal) O. vulgaris were collected over a two year period. Females were found to dominate the intertidal area (sex ratio 2:1), while no difference was found subtidally (sex ratio 1:1). Of those collected intertidally, immature females were most prevalent while males ranged from immature to mature. Mature females were only found subtidally. A marked size difference was apparent, with the subtidal octopus being substantially larger. Although brooding females were found throughout the year, numbers peaked in summer. Individual fecundity ranged between 42,000–790,000 eggs. The total number of eggs produced and the number of eggs per egg string were correlated to female size. Diet did not vary greatly between the inter- and sub-tidal areas, with the main prey items being crustaceans, teleosts and octopus. It appears that the immature females use the intertidal area to feed and grow, before migrating to deeper areas to mature and spawn.

(Received August 8 2002)
(Accepted March 11 2003)


Correspondence:
c1 e-mail: A.Oosthuizen@ru.ac.za