Abstract: Based on the survey data of four cruises by otter trawl in the continental shelf of the northern South China Sea from October 2006 to September 2007, spatial distributions of species composition, species richness D, and catch rate of fishery resource were analyzed. The richest species was found along Zhanjiang transect (405 species), and the fewest species was found along Shantou transect (337 species). Species number showed a skewed normal distribution with the water depth, and more species were found at depths of 40—80m. The trend of spatial distribution of species richness D was the same as the species number. In the total catch, weight composition of the three groups of fish, cephalopoda, and crustacean was 80:12:8. For the transects distribution, the highest ratio of fish in the composition was found along Zhujiang transect, the highest ratio of cephalopoda was found along Zhanjiang transect, and highest ratio of crustacean was found along Yangjiang trasect. For water depths distribution, the composition of fish increased with depth, a higher composition of cephalopoda was found at 40—100m, and the compostion of crustacean at 10—20m was distinctly higher than at other depths. There were six main dominant species in fish. Of the dominant species, Nemipterus bathybius was dominant in 90?120m depth, while Navodon xanthopterus in 60—90m, Upeneus bensasi in 60—120m, Daicocus peterseni in 120—200m, Polynemus sextarius in 30—60m, and Harpodon nehereus in 10—30m. For transect distribution, high catch rate of fish was found in the Zhujiang estuary and western Guangdong waters, and the lowest was found along Shantou transect. For depth distribution, fish catch rate increased with water depth. Catch rate of cephalopoda was found higher in western Guangdong and Zhujiang estuary than in eastern Guangdong waters. Cephalopoda catch rate increased with water depth within 100m and decreased below 100m. The highest catch rate of crustacean was found along Yangjiang transect, and was distinctly lower along other transects. By comparison with the exist-ing data, succession of species was distinct after the decline of fishery resources in the northern South China Sea. While the resource of large-scale and well quality species substantially decreased, the resource of small-scale and bad quality species increased obviously. Under the pressure of fishing catch power in coastal waters, the distribution of fish catch rate showed the trend of increasing with depth.

Key words: northern South China Sea, fishery resources, spatial distribution