Reproductive biology of common octopus Octopus vulgaris (Cuvier, 1797), on the Kenyan South coast

Abstract

Abstract                      

Although common octopus catches are increasing globally, lack of information on the species reproductive biology has been a major concern in its management particularly in Kenya. The present study aimed at investigating the reproductive biology of Octopus vulgaris from Shimoni and Vanga in the Kenyan South coast. Sampling was done monthly from November 2010 to November 2012 using traditional fishing spear. For each specimen body weight (BW), total length (TL), dorsal mantle length (DML), ventral mantle length (VML) and gonad weights were recorded. Maturity stages and Gonadosomatic Index (GSI) were determined using standard methods.

A total of 1,599 specimens were collected, 746 males and 853 females. The sex ratio was 1:1.1 (males: females) for both Shimoni and Vanga during the study period. The results of sexual stages of gonads indicated that Octopus vulgaris was breeding year round with spawning peak from June to August. Fecundity estimates ranged from 5,200 to 389,000 oocytes (mean 154,057.61 ± 29,131.97).  Maturity and gonadosomatic indices showed similar annual changes, especially in the case of females. The female length at first maturity (DML _50%) was 10.8 cm, while for the male was 10.5 cm.