Effects of fyke net mesh size and sampling period on the catch of nekton in an intertidal creek
插网网目尺寸及采样时间对潮沟游泳动物采样的影响

The present study was carried out in an intertidal creek in Jiuduansha saltmarsh of the Yangtze River Estuary,China. Fyke nets of two mesh sizes,4mm and 8mm,were applied to determine the effects of mesh size and day-night period on the catch of nekton. Through the sampling of five consecutive 24 h periods,a total of 5476 fish of 16 species and 4982 shrimp of two species were collected. Analyses indicated that mesh size had no significant effect on the species number and abundance of fish caught,but smaller mesh had higher catch rates of crustaceans. More individuals of fish were caught at night than in the daytime for both 4mm and 8mm mesh nets,but more crustacean individuals were caught by day. In the daytime,different mesh sizes had no significant effect on the length distribution of five most abundant nekton species caught by the nets. In night sampling,nets with smaller mesh captured a greater proportion of large individuals of some predominant species(e.g. Synechogobius ommaturus and Exopalaemon carinicauda),but reverse result occurred in other species such as Liza haematocheila. Community structures of nekton in night and day samples were different. Nets with smaller mesh sizes show relatively low sampling precision values.