Reproductive biology of common octopus octopus vulgaris (cuvier, 1797), on the Kenyan South Coast

Abstract

Although common octopus catches are increasing globally, lack of information on the reproductive biology of the species has been a major concern in its management, particularly in Kenya. The present study aimed to investigate the reproductive biology of common octopus at Shimoni and Vanga on the Kenyan south coast. Sampling was undertaken monthly from November 2010 to November 2012 using a traditional fishing spear. The body weight (BW), total length (TL), dorsal mantle length (DML), ventral mantle length (VML) and gonad weight was recorded for each specimen. Maturity stages and gonadosomatic indices (GSI) were determined using standard methods. A total of 1 599 specimens (746 males and 853 females) were collected. The sex ratio was 1:1.1 (males: females) at both Shimoni and Vanga during the study period. Sexual staging of gonads indicated that the common octopus was breeding year round with a spawning peak from June to August. Fecundity estimates ranged from 5 200 to 389 000 oocytes (mean 154 057.6 ± 29 132). The lowest gonadosomatic index values were recorded during the month of September, indicating the end of the spawning period. The female length at first maturity (DML50%) was 10.8 cm, that for the male was 10.5 cm.