Life history characteristics of Astronesthes ijimai (Stomiiformes: Stomiidae) in the East China Sea

With development of new fisheries in the continental slope of the East China Sea, life history information for mesopelagic fishes under fishing pressure is required to better manage the fisheries and understand the ecosystem. Astronesthes ijimai, a representative mesopelagic species, was collected by commercial bottom trawler from 2022–2025 m, and its growth pattern and feeding habit were analysed. Otolith micro-increments were enumerated from 234 individuals with standard length ranging from 108–169 mm, and no distinct zone/boundary was observed in otolith microstructure. The maximum number of increments indicated a short lifespan of less than 1.5 years. The length–weight relationship revealed a negative allometric pattern, and a medium growth rate (0.26 mm/day) was detected through a linear growth model. A completely piscivorous habit was revealed through stomach content analysis. A. ijimai feed on few but relatively large prey with diel vertical migration, of which Bregmaceros sp. overwhelmingly dominated. A small piece of plastic was also ingested by one individual. The revealed life history characteristics provide insight into stomiids ecology. This information contributes to evaluating the potential effects of fishing pressure and a rapidly changing climate on the mesopelagic ecosystem in the deep sea of the East China Sea.