The ovarian development, fecundity and hypothesis on spawning pattern of common cuttlefish Sepia officinalis off Mauritania

Abstract

Cephalopod species have evolved highly flexible spawning strategies, but the extent to which spawning strategy adopted is inextricably linked to the ovarian development. To address the spawning strategy of common cuttlefish Sepia officinalis outside northwest Africa, an analysis of ovarian development and hypothesis on spawning pattern was undertaken for specimens (mantle length of 126–270 mm from stages II to IV) collected from commercial catches off Mauritania during summer months of July and August 2015. It was found that the mature/spawning female S. officinalis covered a wide range of body size, being 148–270 mm ML, and showed non-stop food intake. The gonadosomatic index (GSI) increased steadily with maturity from 2.13% to 13.22%, being higher mean value of 8.65 ± 1.69% at mature/spawning stage. Potential fecundity (PF) increased with female size from 1306 to 3376 oocytes (mean 2327 ± 554.47). The oocytes were developing asynchronously as evidenced by the dominant small oocytes throughout sexual maturation and a bimodal size-frequency distribution of yolk oocytes for animals at maturing and mature/spawning stages. The mature oocytes in ovaries of mature/spawning individuals consistently accounted for less than 1% PF. There were about 770–1966 viable eggs that would be released during the spawning season. These evidences indicate that S. officinalis off Mauritania undergo the asynchronous ovarian development, and adopt a complementary spawning strategy falling somewhere along a continuum between intermittent and multiple spawning to adapt to the nutrient-rich Mauritanian upwelling system.