Abstract: In order to understand the fish resources in downstream section of Qiantang River, a quarterly survey was conducted by on drift-gill-net or fishpots combining with social investigation at Tonglu section, Fuyang section, and Wenyan section from November 2014 to December 2016. The results showed that a total of 56 species were collected, which belonged to 9 orders, 13 families, 42 genera, and Cyprinidae had the largest number of species, which constituted 60.71% of the total species. The dominant species were Tachysurus nitidus, Carassius auratus, Hypophthalmichthys molitrix and Hypophthalmichthys nobilis. The species number and biomass of fish community displayed obvious variation quarterly, with the largest number in the spring of 2015, and the highest biomass in winter. The Margalef diversity index, Simpson diversity index, Shannon-Wiener diversity index and Pielou diversity index also showed obvious variations quarterly,with the range of 1.24 to 2.83, 0.75 to 0.89, 1.73 to 2.53,and 0.56 to 0.74, respectively. The fish community in the survey regions changed obviously compared with the historical records, and the released fish species had become dominant except the local species Tachysurus nitidus and Carassius auratus. In addition, the presence of exotic species and hybrids may pose a potential threat to the healthy development of fishery resources in the study sections.

Key words: fishery resources, dominant species, Qiantang River