Maturation, fecundity and seasonality of reproduction of two commerciallyvaluable cuttlefish, Sepia pharaonis and S-dollfusi, in the Suez Canal

摘要

The cuttlefish Sepia pharaonis (maximum 250 mm mantle length, ML) and S. dollfusi (maximum 150 mm ML) are widely distributed in the Indo-Pacific from the Red Sea to Japan and Australia. They are the primary fishery in the Suez Canal and the most valuable commercial cephalopods in the northern Indian Ocean. However, their reproductive biology, essential for fishery management, is poorly known. Four maturity stages were described using morphology and histology. Based on the proportions of each maturity stage, as well as various maturity indices, spawning was found to take place from March to June for S. pharaonis and January to April for S. dollfusi. The size at maturity for S. pharaonis was 61 and 122 mm ML for males and females, respectively. In contrast, the size at maturity for S. dollfusi was similar in both the sexes (75 and 84 mm ML for males and females, respectively). Fecundity was estimated by counting the number of maturing and mature ova, which varied from 75 to 1525 for S. pharaonis and 30 to 273 for S. dollfusi. The monthly size-frequency distribution of ova provides evidence for the accuracy of the fecundity estimates. The data suggest that reproduction extends over approximate to 6-9 months; this probably represents the latter 1/2-2/3 of the life cycle, and may be typical for sepioid and teuthoid cephalopods.