Yueqing Bay in China supports important marine resources that sustain local fisheries and food security, but increasing anthropogenic pressures and natural environmental changes threaten its biodiversity. This study used morphological identification, COI DNA barcoding, and 12S DNA metabarcoding to assess ichthyoplankton composition and fish spawning patterns. A total of 13,415 eggs and 17,291 larvae were collected using horizontal and vertical plankton nets. Morphological analysis identified 58 taxa, while molecular methods detected 21 species (COI) and 48 species (12S), with an overall total of 105 species from 78 genera and 42 families. Spawning activity showed clear seasonal and spatial patterns, with the highest abundance and diversity in spring and summer, particularly around Ximen Island and the Bay mouth. These areas function as key spawning and nursery grounds. 12S DNA metabarcoding contributed strongly to species detection, especially for cryptic and morphologically indistinguishable larvae, complementing traditional surveys. The findings provide essential baseline information for monitoring fish stocks, protecting critical habitats, and improving fishery management strategies under increasing anthropogenic and climate-related pressures in Yueqing Bay.

Arabella is the second-most diverse genus in the family Oenonidae, with about 50 spe cies known so far. However, until now, there has been no detailed taxonomic information on Arabella species in the East China Sea. In this study, we describe a new species, Arabella gouqi sp. nov., discovered in the sea off Gouqi Island, Zhejiang, China, using integrated morphological and molecular evidence. This species is characterized by the following features: a pygidium with two swollen pads, short notopodial cirri, a bifid ro bust left and a gracile falcate right maxilla I (MxI), short left and long right maxilla II (MxII), a posterior postchaetal lobe shorter than the chaetae, and gradually tapering of the ventralmost chaetae. Phylogenetic analysis based on both COI and 16S rDNA gene sequences showed that A. gouqi sp. nov. forms a distinct, fully supported monophyletic clade. These findings were further supported by substantial Kimura 2-parameter (K2P) genetic distances between the new species and other reported Arabella species, which ranged from 9.9% to 24.2% for COI and from 5.5% to 25.2% for 16S rDNA. This study provides essential data for understanding the taxonomy of Arabella in the East China Sea and emphasizes the need for further research on this group in the region.