Age and growth characteristic of Sepia officinalis in the West Africa based on cuttlebones.

Common cuttlefish is mainly distributed in the eastern North Atlantic and the coastal waters of Africa, which is an important fishing target for trawl fisheries and the most important commercial species in the Atlantic sepia family. In this study, based on the cuttlefish samples collected from the west Africa coast in July-August 2015, we measured the outer morphological parameters of 283 cuttlebones. Combined with the age information of cuttlebones, we examined the growth characteristics of cuttlefish of different genders. The results showed that there were significant differences in body length and body weight between different genders. The dominant age group of female and male was both 80-100 days. Among the fitting functions of the outer shape of cuttlebone and the age, the logistic function was the best one. The females' maximum likelihood estimates of the outer morphological parameters of cuttlebone were larger than that of males. The absolute and instantaneous relative growth rates of the cuttlebone length and width of male and female cuttlefish peaked at 110-120 days and 100-110 days, respectively. The age of males and females at first sexual maturity was 111 days and 104 days, respectively. The growth difference between genders might be related to environment.