Abstract:In this study we analyzed the spatial distribution and the diversity of the fishery species in the Yangtze River estuary and its adjacent waters, and explored how they are affected by the environmental factors, based on the bottom trawl survey data collected from August 2012 to May 2013. A total of 114 fishery species (17 orders, 66 families and 90 Genera) were collected, including 58 fish species (12 orders, 36 families and 50 Genera), the richest species was found in Perciformes (26 species), 49 crustacean species (2 orders, 25 families and 33 Genera) and 7 cephalopod species (3 orders, 5 families and 6 Genera). The dominant species were season-dependent, whereas Harpodon nehereus was the only all-year-round dominant species. The average catch per haul was highest in autumn (29.20 kg/h·net), followed by that in spring (17.95 kg/h·net), summer (14.60 kg/h·net), and the least in winter (10.15 kg/h·net). Generally the demersal fish and crustaceans constituted the majority in the catch in all seasons, and the percentage of the pelagic fish was only slightly higher in spring (20.1%). The diversity indices of fishery species in spring and summer were higher than those in autumn and winter. The migration index and alternate index of fishery species were higher in spring (163) and summer (176), which meant the higher stability in fisheries community in the Yangtze River estuary. The migration index was close to 0 in summer (6) and winter (–5), suggesting that the immigration and emigration of the fishery species were in a state of balance. The number of fishery species and total catches were significantly positively correlated with the catches of the demersal fish and the crustaceans respectively in all seasons (P<0.01). The number of fishery species in autumn was positively correlated with both the sea surface temperature (P<0.05) and the water depth (P<0.01). These results showed a trend of increase in the low-valued species in the Yangtze River estuary and the adjacent waters. Our study suggested that there were significant seasonal variations in the structure of the fishery resource, and that the number of fishery species, the total catches and the diversity indices were highly related to the sea surface temperature and water depth.
