Early Life Resources Community Structure and Functional Diversity of Osteichthyes in the Waters Adjacent to the Changdao Islands

Abstract

The waters adjacent to the Changdao Islands are a key gateway for fish recruitment and 0-year-old juveniles migrating between the Yellow and Bohai seas, and there is a lack of local observations of early life history characteristics of fish in this area. To investigate monthly variations in the abundance, community structure, and functional diversity of early life resources of fish in waters adjacent to the Changdao Islands, monthly surveys were conducted from March to December, 2021. This study examined the spatiotemporal patterns of the early life resource abundance of fish in waters adjacent to the Changdao Islands using data on fish eggs, larvae, and the environment, and analyzed monthly variations in community structure and functional diversity. Spatial interpolation, Garrison centroid, and similarity percentage analysis methods were employed, along with functional trait indices. A total of 36 early life fish resource species comprising 21 separate species of fish eggs and larvae were collected from waters adjacent to the Changdao Islands between March and December 2021. The total quantity of fish eggs was 71, 695, and that of larvae was 1, 161. The main spawning period was from May to August. The main spawning species were Engraulis japonicus, Nibea albiflora, Saurida elongata, Acanthopagrus schlegelii, Sillago japonica, Pennahia argentata, Callionymus beniteguri, and Cynoglossus joyneri. The dense area of fish eggs was situated in the waters adjacent to the Miaodao Strait, extending from the eastern to southwestern waters of the study area. The main distribution period of fish larvae was from May to July and from November to December. The main larval species were E. japonicus, Hypoatherina valenciennei, Hexagrammos otakii, and Ammodytes personatus. The dense area of fish larvae was situated in the eastern, southwestern, and northwestern waters of the study area. The richness, evenness, and dispersion indices of early life resources community structure and functional diversity of fish were highest during the spring-summer season (May to July). In the northeast and southwest regions of the study area, there were abundant early life fish resource species with high functional richness and divergence, and moderate evenness. Local fish communities have strong resistance to disturbance, and the recruitment of fish transported from this area can occupy a large ecological niche in spawning grounds, thereby promoting the ecological resilience of early life fish resource communities. In the summer-autumn (August to September) and autumn-winter (October to December) seasons, as the spawning season of migratory fish comes to an end, there was a significant decline in the number of early life fish resource species. This led to a reduction in the ecological niche space and a decrease in the functional diversity of early life fish resource communities in the waters adjacent to the Changdao Islands. In conclusion, the abundance, community structure, and function of fish eggs and larvae in the waters adjacent to the Changdao Islands exhibited significant spatiotemporal heterogeneity. The migration of reproducing fish populations also appeared to have a profound effect on the early life fish resource communities in the waters adjacent to the Changdao Islands. Community structure is mainly influenced by the migration of spawning herring, and the dominance of warm-water species, such as Cynoglossus joyneri and Sillaginidae species, increases in the summer. This indicates that the succession pattern of early life fish resource communities in the waters adjacent to the Changdao Islands shares common characteristics with the spawning grounds in the central-northern Yellow and Bohai seas. In addition, compared with seawater spawning grounds with intact coastlines, large water depth gradients, and relatively stable currents, the dense areas of early life fish resources in the waters adjacent to the Changdao Islands during the warming period in the spring-summer season are relatively scattered. The stability of the community is greatly affected by the spawning and migration of fish, and there is a significant difference in the spawning intensity of recruitment groups. As an area adjacent to island groups in the Yellow and Bohai seas and as a migratory channel for fish, the early life fish resources in this region have distinct features. The abundance and diversity of early life fish resources in this area may reflect the characteristics of local communities, as well as the stability of new communities formed by recruitment groups transported from this area to spawning grounds. Therefore, mastering the annual succession pattern of early life fish resource communities in waters adjacent to the Changdao Islands is conducive to an overall understanding of the early life history of fish in the central-northern Yellow and Bohai seas, and facilitates a deeper understanding of the fish population recruitment process in adjacent waters of temperate island ecosystems. Research on the early life history of fish in the waters adjacent to the Changdao Islands should not be limited to a traditional spawning site perspective. The intermediary centrality of this area in the fish migration network of the Yellow and Bohai seas is also worth highlighting.

Keywords

• osteichthyes
• waters adjacent to the changdao islands
• early life resources of fish
• population recruitment
• community functional diversity