渤海对虾流网作业中掉虾数量及其成活率的研究

DROP AND SURVIVAL RATES OF PRAWN CAUGHT IN DRIFT—NET OPERATING IN BOHAI SEA

根据对虾流网结构特点设计兼有捕虾和接获网上掉虾功能的专用网具,研究了对虾流网作业全过程的掉虾数量;同时还对暂养模拟掉虾和对虾在网上直接死亡率作了调查;并研究了流网掉下对虾的成活率。所得结果为调整渤海区秋季对虾汛的捕捞结构,实行以流网代替拖网作业的管理决策提供了科学依据。

Dropped quantity of prawn (Penaeus orientalis) caught by drift netwas studied in a whole course of fishing operation. The net used was designed ba-sed on the structure feature of prawn drift net and the net had the function bothof catching prawn and receiving dropped ones. The survival rate of prawn whichdropped from the meshes of drift net was also studied. 1. In the whole course of menually hauling drift net on board the small boat of12 hp., the drop rate of prawn accounted for 40-74% of the total number of prawncaught in one haul. And the drop rate of 13-33% was reached in the course ofmechnically hauling on board of the large boat of 120 hp. 2. Through simulating test,it was found that the survival rate of prawn,whichwere picked up from a drift net by hand and cultured for 24 hrs,reached a level as high as more than 93%, while the immediate mortality of prawn found in net wasbelow 8%. There were a considerable number of scarred prawn appeared in the catch bydrift net, and it has proved that the dropped prawn could survive and enter intorecruitable population. The above results provide some scientific information for regulating the fishi-ng structure in the autumn season in Bohai Sea, and making management stra-tegy of gradually replacing prawn trawling by drift net operation.