Variation in the Occurrence of Salp and Doliolid Assemblages in the Northeastern East China Sea from 2019 to 2023

This study characterizes the distribution of salp and doliolid species in the northeastern East China Sea during spring and autumn and identifies the factors that regulate their abundance. The data were collected over four years (2019–2023, except 2020). During the survey period, the Tsushima Warm Current Surface and Bottom (TWCS and TWCB, respectively) and Yellow Sea Cold Bottom Water were influential in spring, while the Changjiang Diluted Water, Coastal Water, TWCS, and TWCB were dominant in autumn. The mean sea surface temperature (SST) and sea surface salinity (SSS) in spring and the mean SST in autumn statistically decreased (p < 0.05), while the mean SSS in autumn statistically increased (p < 0.05). The spatial distribution of salp and doliolid species remained consistent in spring and autumn, although the dominant assemblage shifted seasonally. Spring was predominantly characterized by an abundance of salp species, whereas doliolid species were dominant in autumn, with their distribution and abundance influenced by different environmental factors such as temperature and salinity in spring and food availability in autumn. Our results provide valuable data on the factors affecting the presence of salp and doliolid species in the northeastern East China Sea.