Effects of environmental variables on the interannual variability of early growth of Trichiurus japonicus in the East China Sea

The biological traits of largehead hairtail ( Trichiurus japonicus ) in the China Seas have undergone pronounced changes, such as smaller body length at age and earlier maturation, which may be attributed to environmental shifts. Consequently, clarifying which environmental variables play a decisive role in the early growth stages of largehead hairtail, along with their impacts, is indispensable for understanding the early life history of this species, and it also holds significant ecological and socio-economic value. To comprehend the variations in early growth of largehead hairtail, we investigated the temporal-scale influences of environmental changes on its early growth. In this study, based on the samples from the East China Sea from 2017 to 2021, the specific relationships between early growth and environmental variables were analyzed by otolith microstructure. Our investigation revealed a notable interannual variability in the early growth of the population. Notably, the sea water temperatures during March and April of 2018 were anomalously lower compared to other years, which corresponded with better growth performance, aided by the reduced Mixed Layer Depth (MLD) during this period. Post-2019, the growth conditions in May were predominantly more conducive for the early growth than in April, leading to a shift in the occurrence of growth peaks to the month of May. This research will provide a foundational understanding of the adaptability of largehead hairtail in the East China Sea in the face of climate change, offering theoretical support for the scientific management of fishery resources. • Environmental changes drive interannual differences in the early growth. • Growth promotion by temperature peaks at 20–22.5°C SST and weakens with further warming. • Drops in average and peak growth are evident in the warmer years. • Shifted growth phenology demonstrates adaptive plasticity to climate shifts in the early life stages.