A review on fishing gear in China: Selectivity and application

In the 1980s, China's offshore marine fishery resources declined, thus fishing gear selectivity gradually became a focus of scientific fishery research. Studies of fishing gear selectivity mainly focus on five kinds of fishing gear: trawls, shrimp beam trawls, stow nets, gillnets, and pots. Cover net method is the main method used in the comparative study of codend selectivity of both trawls and stow nets. These results showed that (1) Bottom trawls, targeting Larimichthys polyactis (the Little yellow croaker) and Trichiurus haumela (the Hairtail), should have a minimum mesh size of the codend no less than 60 mm in the Yellow and East China Seas. While the codend should use a square mesh with a minimum mesh size of 40 mm due to the variety of targeted species in the South China Sea. (2) Pair pelagic trawls, targeting pelagic species such as Engraulis japonicus (the Japanese anchovy), Pampus argenteus (the Silvery pomfret), Scomberomorus niphonius (the Spanish mackerel), as well as bottom species such as L. polyactis and T. haumela, should have a minimum mesh size of the codend no less than 56 mm in the Yellow Sea. (3) Shrimp beam trawls should use shrimp/fish separator devices (e.g., separator panels, vertical separator panels, and sorting grids) to improve intra-species selectivity and reduce by-catch of non-target fish. (4) Canvas stow nets, targeting L. polyactis and T. haumela, should have a minimum mesh size of the codend no less than 55 mm. (5) Gillnets, the minimum mesh size should be determined for catching traditional economic species, but also the optimal mesh size for newly developed species. Such as, gillnets with mesh size of 35–38.71 mm targeting Harpodon nehereus (the Bombay duck), 55 mm targeting L. polyactis and Nemipterus virgatus (the Golden threadfin bream), 72 mm targeting Dentex tumifrons (the yellow sea breams) or Scomberomorus commersoni with body length of 280 mm, 100 mm targeting P. argenteus, 104 mm or 146 mm targeting 2–3 year or 6–7 year S. niphonius, 120 mm targeting S. commersoni with body length of 380 mm, and 144 mm targeting Pampus chinensis (the Chinese pomfret). (6) Pots, the steel-framed round pots targeting Portunus trituberculatus (the swimming crab) should have a 33 mm height of escape vent or an 8 cm diameter escape hole, and the steel-framed round pots or accordion-shaped trap targeting Charybdis japonica (the Asian paddle crabs) should have a 30 mm height of escape vent installed on the side of pots. These results of fishing gear selectivity from the scientific basis for the implementation of fishing gear access systems, especially for identifying the minimum mesh size of fishing gear. In the future, the Fisheries Research Institute of China should conduct long-term investigations of selectivity in trans areas. Developing fishing gear access systems that are in line with a sustainable development is of great significance for the conservation and restoration of offshore fishery resources in China.