Age, growth parameters, and reproductive characteristics of the sharpspine skate (Okamejei acutispina) in the East China Sea

Abstract

— The sharpspine skate ( Okamejei acutispina ) is a commercially exploited skate species in the East China Sea, and it is suspected that the population of this species in this region has declined due to fishing pressure and other factors. Nonetheless, information on its life history, which is essential for population assessment and management, is limited. We estimated its age, growth, maturity, and egg-laying season on the basis of data for 331 specimens captured in the East China Sea. Age was determined by counting translucent bands on vertebral centrum sections. Maximum total length (TL) and age were 448 mm and 10 years for females and 444 mm and 9 years for males. Among the 3 growth models applied to length- at-age data, the von Bertalanffy growth function provided the best fit for both sexes (females: theoretical asymptotic length [ L ∞ ]=428 mm, growth coefficient [ k ]=0.30, and theoretical time a zero length [ t 0 ]=−1.04 years; males: L ∞ =422 mm, k =0.31, and t 0 =−1.04 years). Size and age at 50% maturity were 380 mm TL and 4.60 years for females and 357 mm TL and 4.21 years for males. The monthly seasonal reproductive data, including egg case occurrence and oocyte maximum diameter, indicate a prolonged egg-laying season. Our findings indicate that the life history of the sharpspine skate in the East China Sea is characterized by a shorter lifespan, faster growth, and earlier age at maturity than many other skates globally.