ASSESSING FISH ASSEMBLAGES IN A SHALLOW YANGTZE RIVER LAKE USING MULTI-MESH GILLNETS AND DENSE-MESH WEIRS

To assess possible bias of different fishing methods is essential to appropriate fisheries management. In the current study, fish assemblage structure of a shallow Yangtze River lake was assessed by combining one international standard sampling gear (multi-mesh gillnet), and one traditional Chinese gear (the dense-mesh weir). Using Lake Biandantang as a case study, a total of 27 fish species were collected from the two gears combined, including 2 new species that had not been recorded previously in this lake. Results suggested that fish assemblages had changed greatly compared to a previous study conducted in the 1990s. Specifically, differences were found in species composition, abundance, biomass, and length distributions collected from the two gears. Difference in total length (TL) distributions of fishes caught was the most conspicuous change. Fishes collected from the weir ranged from 40—70 mmTL, whereas fishes collected from gillnets ranged from 90—140 mmTL. Multivariate ordinations based on relative abundance and biomass data also indicated fish assemblage structural differences between the two gears. The comparative results showed that the multi-mesh gillnet was effective at assessing fish assemblages in shallow lakes, such as those found along the middle and lower reaches of the Yangtze River. Additionally, assessments using only one gear could have some limitations with respect to interpreting fish assemblage changes over time.