Community structure of early life stage fish resources and its relationship with environmental factors in the Western waters of Sishili Bay, Yantai

Sishili Bay, Yantai, is located in the northern waters of Laishan District, Yantai City, adjacent to the North Yellow Sea, bordered by Zhifu Bay to the northwest and connected to the Yangma Island waters to the east. It is one of the important coastal bays in the Yantai-Weihai coastal area. To investigate the environmental driving mechanisms governing the dynamics of fish early life stages and to evaluate the effects of artificial habitat modification on recruitment processes in Sishili Bay, Yantai, this study was based on ichthyoplankton survey data from nine cruises conducted between 2024 and 2025. We employed the relative importance index, species turnover rate, and diversity indices to analyze intra-annual variations in community structure; utilized Canonical Correspondence Analysis (CCA) and Mantel tests to examine the spatiotemporal distribution patterns of fish eggs and larvae and their relationships with environmental factors; and applied Mann-Whitney U tests to analyze differences in basic environmental parameters between artificial reef and control areas, while comparing species dominance and average resource density to assess the current impacts of artificial reef construction on the distribution of fish early life stages. Results showed that a total of 21 fish egg taxa and 33 larval fish taxa were recorded, with the primary spawning period occurring from May to July. The dominant spawning species included Kareius bicoloratus, Paralichthys olivaceus, Konosirus punctatus, Engraulis japonicus, Sillago japonica, Sebastes vulpes, Sardinella zunasi, Hyporhamphus sajori, Hypoayherina valenciennei, Strongylura anastomella and Hexagrammos otakii, among 20 species. Species composition, resource density, and species turnover rates all exhibited distinct monthly variations, with inter-monthly turnover rates remaining no less than 47%. Cold-temperate and warm-temperate fish species coexisted from March to May, warm-temperate and warm-water species dominated from June to August, and a transition from warm-water to cold-temperate species was observed from September to November. For fish eggs, both the Shannon-Wiener diversity index (H′) and Pielou's evenness index (J′) displayed trends of initial decrease, followed by increase, and subsequent decrease, while the Simpson's diversity index (D) peaked in May and then fluctuated downward. For larvae, H′ exhibited an increasing then decreasing trend, D showed an initial decrease followed by increase and then continuous decline, whereas J′ peaked sharply in September before dropping rapidly. Sea surface temperature and salinity were identified as the key environmental drivers of the spatiotemporal patterns of fish early life stage communities. Current artificial reef construction demonstrated significant associations with the aggregation of early life stages of certain reef-associated species (Acanthopagrus schlegelii and Sebastes vulpes). These findings provide scientific basis and ecological data support for the assessment and conservation of fish early life stages and the evaluation of ecological benefits of artificial reefs in the western waters of Sishili Bay.