Abstract:Common cuttlefish (Sepia officinalis) is one of the most important economic and ecological species in the West African coastal waters. Studying the morphology and growth characteristics of its beak is beneficial for common cuttlefish´s development and utilization. This study analyzed beak morphological parameters and their ratios based on the samples collected by the Chinese trawlers in 2015 in coastal waters of West African Mauritania, and studied the beak growth variations in different mantle length groups and different gonadal maturity stages. Morphological parameters of beaks were used to estimate the size of the cuttlefish. The results showed the length ratio indices of the lower beak were not stable, and that the beak morphological parameters of female were significantly higher than the male after eliminating the effect of the sample size differences by dividing the mantle length (P<0.01). The ANOVA and the Least Significant Difference (LSD) analysis showed that morphological parameters of the common cuttlefish beaks significantly increased with the growth of mantle length (P<0.01) and gonad maturity stage Ⅱ~Ⅳ (P<0.01). However, beaks in the gonad maturity stage V were significantly smaller than those in the previous periods (Ⅱ~Ⅳ, P<0.05). Principal component analysis showed that upper hood length (UHL) and lower crest length (LCL) had the highest loading coefficient in the first principal component, and that lower rostrum length (LRL) and lower rostrum width (LRW) had the highest loading coefficient in the second principal component, which can be used for the mantle length estimation. This study provides basic biology information for the classification and ecological research about common cuttlefish in the coast of West Africa.
