Taxonomic and functional diversities reveal different fish assemblage dynamics of stow net fishery in Haizhou Bay

Biodiversity is the cornerstone of marine fisheries. To ensure the prosperity of stow net fishery in Haizhou Bay, regular investigations of fishery resources are essential. However, most studies have primarily focused on taxonomic diversity while overlooking functional diversity. In this study, we examined both the taxonomic and functional diversity of fish assemblages based on abundance and functional traits from 2013 to 2018. Significant differences in taxonomic diversity were observed only between two seasons, whereas functional diversity showed significant differences across years, seasons and groups. Diversity indices exhibited negative linear relationships with catch per unit effort, except for functional evenness (FEve) and functional divergence. Twenty-seven out of 30 correlations between the two types of diversity indices were predominantly positive and synclastic, whether linear or nonlinear. Functional dispersion showed the most positive relationships with taxonomic diversities, while FEve exhibited gentle slopes. The functional redundancy curves indicated that the ecological stability and resilience of fish assemblages were vulnerable. The non-target fish group demonstrated a higher overlap in functions compared to the target fish group and the total fish group. In summary, the taxonomic and functional diversities revealed inconsistent statuses and trends of fish assemblages, with an evident decreasing trend in the non-target fish group requiring special attention. This study highlights that both taxonomic and functional diversity should be considered simultaneously in fish biodiversity investigations, which is crucial for establishing effective fish conservation systems.