Comparative age and growth of Uroteuthis chinensis and Uroteuthis edulis from China Seas based on statolith

To determine the age and growth of Uroteuthis chinensis and U.edulis,growth increments of the lateral dome of the statolith were used in the present study.Specimens of the two species caught in the South China Sea(SCS)and East China Sea(ECS)were used to compare the age and growth differences between sexes.In the present study,we found the two species have similar lifespans of less than 200 days.We also found that there were significant differences in the relationships between mantle length and body weight for two species and for both sexes in the same species.The back-calculated hatching date for the two species was similar,i.e.October to January for specimens caught in spring,and March to June for specimens caught in summer(U.edulis)or autumn(U.chinensis).Exponential and logistic growth curves were fitted to build the age and mantle length relationship.Both growth curves showed that U.chinensis has a larger mantle length than U.edulis at the same age.The results of the growth rates also showed that U.chinensis grows faster than U.edulis.However,there are discrepancies between previous studies and the present study on the lifespan of the two species.Also,the sample size of the present study is small especially for U.edulis.Hence,future studies should be conducted to validate the daily periodicity of growth increment in the regions of statolith(except for the lateral dome which has been validated)and the sample size should be increased for age and growth studies.