Development trend of trawl fishery and its impact on fishery resources in South China Sea

Trawl is the most important fishing gear in the marine fishery production of the South China Sea, in which trawl fishery occupies a dominant position. The number of trawlers increased from 6 730 in 1986 to 14 599 in 2003, then dropped and had remained at about 9 000 since 2010, with the gross tonnage of trawlers ranging from 212 864 t to 876 045 t, showing a steady increasing trend. However, the total power of trawlers increased from 440 438 kW in 1986 to 1 735 173 kW in 2005, and then showed a decreasing trend. The average tonnage and power of single vessels showed a significant increasing trend from 1986 to 2020, and the yield of trawl fishery ranged from 59.24×10⁴ t to 181.66×10⁴ t, accounting for 38.35%–62.96% of the total fishing production in the South China Sea with a decreasing trend. The yield per kilowatt ship and per ton ship ranged from 0.72 to 1.40 t and from 1.18 to 3.90 t, respectively, both were highest in 1999 and then showed a decreasing trend. According to the statistical results of the proportion of juveniles of eight important economic fish species, the proportion of juvenile biomass and average proportion of quantity in the trawl catches from 1992 to 2020 was 24.35%–84.28% and 40.09%–89.84%, respectively. Pennahia argentata, Trichiurus japonicus and Trachurus japonicus had the highest proportions of the juveniles. In view of the low selectivity of trawl fishery, it has a great impact on juvenile fish resources and marine environment. We propose to gradually reduce the size of trawlers, strictly implement the system of mesh size and catching specification, and guide fishermen to use resource-saving and environmentally friendly methods of operation, so as to promote the conservation and sustainable use of offshore fishery resources.