Objective This study aims to assess the composition and biodiversity of fishes in Futun River by analyzing the results of the 2023 fish community survey and comparing them with historical data. Insights into biodiversity, including species composition, dominant and common species, and ecological types, were obtained.

Methods The fish resource sampling survey was conducted in Futun River from February to December, 2023. Fixed three-layer gillnets and folding funnel traps were employed as fishing tools. Morphological data, such as body length and body mass, were recorded. Ecological indices, including relative abundance, index of relative importance (IRI), Margalef richness index, Shannon-Wiener diversity index, and Pielou evenness index, were utilized to evaluate the diversity of the fish community. The data collected from each sampling site were processed and analyzed using statistical analysis software.

Results The survey recorded 56 species across five orders and 13 families, indicating a significant decline in species number and notable shifts in composition since 1984; however, Cyprinidae remained prevalent. Three nationally protected species, including Anguilla marmorata, were absent from the survey. Using Pinkas’ IRI index, three species, including Sinibrama macrops, etc., were identified as dominant, while nine species, such as Acrossocheilius hemispinus, etc., were recognized as common. Biodiversity indices revealed the highest Shannon-Wiener diversity index at site S2 (2.95) and the lowest at site S4 (1.39), with the Margalef richness index peaking at site S2 (4.89) and dipping at site S1 (2.12).

Conclusion The research findings indicate significant changes in the structure of the fish community in Futun River. These changes are characterized by a reduction in the total number of species, the continued dominance of Cyprinidae, the absence of certain protected species, and the increasing impact of alien species on the local community, highlighting the urgent need for ecosystem protection.