The common octopus Octopus vulgaris is the most important demersal species in landings from the whole Gulf of Cádiz. Monthly samplings from trawl and artisanal gears were carried out in 1996, due to the remarkable multifleet nature of the octopus fishery in the study area.
Yearly sex ratio was estimated as 1.06:1 (male:female). There were no significant seasonal differences in the sex ratio. A four stage maturity scale was used for both sexes. The reproductive period was determined from the monthly evolution of these stages as well as that of several maturity
and condition indices. The breeding season extended from February to October, with spawning peaks in April–May and August. Dorsal mantle length and body weight at maturity were estimated at 17.6 cm and 2023 g for females and at 10.4 cm and 671 g for males. Mature males occurred throughout
the year. Total fecundity ranged between 70,060 and 605,438 oocytes (mean = 315,197 ± 135,865). Residual oocytes represented 6.2% on average of the total of ovarian oocytes. The maximum number of fully developed spermatophores was 276 in a male of 21 cm and 3350 g. The mean length of
mature spermatophores in mature males was 51.3 mm (±10.2).
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