An exploratory fishing survey of light falling-net fisheries in the central and southern South China Sea in autumn

Based on the survey data from September to October in 2012, we analyzed the fishing ground and catch composition of large-scale light falling-net fishery in the central and southern South China Sea in autumn. According to the index of relative importance ( IRI) , Sthenoteuthis oualaniensis and Katsuwonus pelamis were the dominant species; Euthynnus affinis, Auxis thazard and A. rochei were the major species; Decapterus macarellus and D. macrosoma and so on were the common species. Generally, S. oualaniensis, tuna species and round scad were the main species which accounted for 48.35% , 48.33% and 0.98% of the total catches, respectively, and small tunas occupied 47.77% of the total. The catch rate varied significantly among different fishing grounds, which was 411.47 kgh-1 in Xisha and Zhongsha waters but only 25.66 kgh-1 in Nansha waters. The central fishing ground was located in waters of 1230N～1530N, 11030E～11500E. The results indicate that autumn is a very good fishing season for light falling-net in offshore waters. Besides, S. oualaniensis and larger tuna species, small tuna species and round scad should be further studied.