| In order to improve the fishing techniques and management level of offshore fishery resources and promote the implementation of the National Marine Fishing Gear Catalog, gillnets fishery wereinvestigated insome fishing ports and fishing villages around the coastal of the Yellow Sea and Bohai Sea during July and August in 2014. Results showed thatthere were 17 kinds of common gill nets including 8 kinds of single gill nets and 9 kinds of triple gill nets in the 11 fishing ports and fishing villageswhere we investigated, and the main dimensions of the nets were various. The main economical fishing targets in Yellow Sea and Bohai Seawere Scomberomorus niphonius,Pseudosciaena polyactis,Portunus trituberculatus,Oratosquilla oratoria,Tenneropenus chinensis,Rhopilema esculentum Kishinouye, and so on. Selectivities between single gillnets,double gillnets, triple gill nets and production gillnetswith the mesh sizes 40 mm, 50 mm and 60 mm were compared during September and November in 2014. And the result provided a reference for the triple gill nets whether could they be used after the transitional period.The results of experiments in Yellow Sea showed that catch species were similar in different kinds of trial nets with different mesh sizes while the dominant species were different. CPUE of the triple gillnets with each mesh size were 187%, 174% and 146% comparing with the single gillnets with the same mesh size while economic benefits of the triple gillnets were 133%, 112% and 184% comparing with the single gillnets. The juvenile Pseudosciaena polyactis proportion of the triple gillnets were 162%, 342% and 122%comparing with the single gillnets, while the juvenile Cleisthenes herzensteini proportion were 108%, 277% and 100%. The catch composition showed that selectivity of the single gillnets was better than the triple gillnets for fusiform fish, and the catching ability of the triple gillnets was better than the single gillnets for Lophius litulon and Cleisthenes herzensteini.The results of experiments in Bohai Sea showed that the main catch species of each kinds of nets were basically the same, and the number of the catch species was between 6 and 9. The dominant species of experimental and producting fishing gear were Oratosquilla oratoria(dominance decreased with the increasing mesh size)and Lateolabrax japonicus(dominance increased with the increasing mesh size). Catch yields of the same type nets with different mesh sizes were different. Comparing the CPUE of the 60mm-size-net with the 40mm-size-net, we found that the single gillnet was 800%, while the double gillnet was 650% and the triple gillnet was 500%.With the increasing mesh size,the proportion of the catch the juvenile fish was decreased. The influence on the catch yields of different types nets with the same mesh sizes was relatively small, while the Oratosquilla oratoria catch yields of these three kinds of gill nets were significantly different(P=0.04,P=0.66×10-6,P=0.029). The proportion of Oratosquilla oratoria catch increased with the single gillnets, double gillnets and triple gill nets. The number of the Oratosquilla larvae increased withthe single gillnets, double gillnets and triple gill nets while the proportion of the Oratosquilla larvae was not significantly different. For fusiform fish such as Pseudosciaena polyactis, Scomberomorus niphoniusand Lateolabrax japonicas,single gillnetswere better than double gillnets and triple gill nets. And for crustaceans and flatfish, triple gillnets were better than double gillnets and single gillnets.Currently, the triple gillnets are widely used in Yellow Sea and Bohai Sea. For Oratosquilla oratoria, Portunus trituberculatusand other crustaceans fisheries, the single gillnetscould not replace the triple gillnets. Therefore, we suggest to list the triple gillnets into permitted fishing gears and limit the minimum mesh size to 60 mm. Thus, we can not only conservethe fishery resources, but also maintain a stable fisheries. |
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