Catch composition of monofilament gillnet netting with different mesh sizes in Qingcaosha Reservoir, Shanghai, China

During 2010 to 2012, fish diversity in Qingcaosha Reservoir was studied based on gillnets (multi-mesh monofilament gillnets and single-mesh trammel gillnets), electric fishing, bottom trawl and cage. The investigation collected a total of 34 fish species, belonging to 8 orders, 12 families. Cypriniformes contained the largest number of species (19 species) in the collection, followed by Perciformes (6 species). Multi-mesh monofilament gillnets sampled 19 fish species, of which Coilia nasus was the dominant species. Hierarchical cluster analysis indicated that mesh size of monofilament gillnets had significant influence on the composition of catches: C. nasus and Hemiculter bleekeri were the dominant species of catches of gillnet netting with mesh size of 2 cm, while C. nasus was the dominant species of catches of the nettings with mesh sizes larger than 2 cm. Species numbers and the catch per unit of effort (CPUE) had a decreasing tendency with the increasing mesh size. Mesh size also had significant effects on the total length distribution of the dominant species C. nasus, which increased with the increasing mesh size. The results suggested that a combination of several gears was required to reliably estimate fish diversity of standing waters.