Deciphering age, growth and maturity patterns in one of the smallest but data‐deficient shark species, slendertail lanternshark (<scp><i>Etmopterus molleri</i></scp>), from the East China Sea

Deep-sea sharks represent a vulnerable group due to their unique life-history traits, including slow growth and late maturity. This study aims to fill knowledge gaps on key demographic parameters of Etmopterus molleri, a lanternshark species, one of the smallest shark species recorded, classified as 'data deficient' in the East China Sea. A total of 280 specimens (165 females and 115 males) were analysed to estimate age, growth and sexual maturity. Post-cranial vertebral section was treated with cobalt nitrate hexahydrate for improved age determination. Age estimation from band pair ranged from 0 to 13 in females and from 1 to 12 in males [coefficient of variation (CV) = 2.27%, average percent error (APE) = 1.60%]. The von Bertalanffy curve with the Bayesian growth Markov chain Monte-Carlo (MCMC) models using observed and back-calculated data provides the best-fit estimation compared to all models, demonstrating an asymptotic length of L_∞ = 391.61 ± 10.06 mm for males and L_∞ = 486.28 ± 14.71 mm for females, with a common birth size (L₀) of around 100 mm. The growth completion rates were (k) of 0.16/year for the males and 0.11/year for the females, marking sexual dimorphism, with females reaching larger sizes (L₅₀ = 287.78 mm) and maturing later (A₅₀ = 6.57 years) than males (L₅₀ = 260.33 mm, A₅₀ = 4.77 years). This maturity life strategy, typical of deep-sea elasmobranchs, underscores the vulnerability of E. molleri. A prudent management approach and continuous monitoring are essential for collecting more data to understand their ecology and preserve their fragile future.