Catch composition and spatial-temporal distribution of catch rate of light falling-net fishing in central and southern South China Sea fishing ground in 2017

Based on the light falling-net fishing data in the fishing grounds in the midwest South China Sea upwelling and northeastern Nansha island-reef area in spring and autumn of 2017, we analyzed the catch composition, biological characteristics of the main species and distribution of the catch rate. Sixty-nine species were identified. In upwelling fishing ground, there were 36 species in spring and 38 in autumn. In island-reef fishing ground, there were 35 species in spring and 43 species in autumn. In upwelling fishing ground, the dominant species (IRI>1 000) were Symplectoteuthis oualaniensis, Decapterus macarellus and Coryphaena hippurus in spring, and S.oualaniensis, D.macrosoma, Auxis tapeinosoma, Brama japonica and A.thazard in autumn. In island-reef fishing ground, the dominant species were S.oualaniensis and D.macarellu in spring, and S.oualaniensis and A.thazard in autumn. In upwelling fishing ground, the average catch rates in spring and autumn were 179.64 kg·h^–1 and 553.41 kg·h^–1, respectively, while 94.55 kg·h^–1 and 382.46 kg·h^–1 respectively in island-reef fishing ground. The distribution of mantle length (fork or body length) and body mass of major species were different in spring and autumn; most of these species had a high proportion of young fish. Thus, young fish should be protected to ensure the sustainable development and utilization of fishery resources in the South China Sea.