Reproductive cycle and energy allocation of Octopus vulgaris in Galician waters, NE Atlantic

Abstract

Reproductive and energy allocation analyses were performed on 1418 common octopus (Octopus vulgaris) from the Galician creel fishery (NE Atlantic) between May 2000 and December 2005. Individuals ranged from 8 to 35 cm dorsal mantle length (DML) and 136–6303 g body weight (BW). The length–weight relationship for whole animals was BW= 2.9(±1.1)×DML2.17(±0.04) (r = 0.86; P < 0.00001). The sex ratio only differed from 1:1 during May and September. Spawning of O. vulgaris in this area extends from December to September with a unique peak in spring months. Size-at-maturity was 1788 g for females (n = 508); and 903 g for males (n = 467). Mean (±S.D.) potential fecundity was estimated at 221,447±116,031 oocytes and mean oocyte length at 3.0±0.8 mm. The mean number of fully developed spermatophores was 182±88 with mean length of 48.8±10.6 mm. Potential fecundity was significantly correlated with length and weight in both sexes. The condition (digestive gland to body weight ratio) of females increased proportionally with maturity stage and mature individuals had higher gonad investment suggesting that energy for gonad growth was derived from the diet rather than endogenous reserves. On the other hand, mature males showed poorer condition. The general picture of the reproductive biology of this species in Galician waters is discussed taking into account the seasonal wind-driven upwelling that governs this ecosystem.