拖网作业参数对南极磷虾捕捞效率的影响

为了解南极磷虾(Euphausia superba Dana)拖网作业中捕捞效果及影响因素,根据 2017 年 12 月 2018 年 6月随“龙腾”轮在南极海域生产时收集的作业参数、网具深度和声学数据等信息,利用声学方法获取磷虾集群质量中心深度与期望入网渔获量,结合网位变化和渔捞统计情况量化捕捞效率;利用广义可加模型(GAM)分析不同拖速和曳纲长度下,网位与磷虾集群质量中心的偏离程度,研究其对网具捕捞效率的影响。结果表明:(1)磷虾集群质量中心水深为(37.29±9.72) m,拖网稳定拖曳期间网位深度为(30.72±10.41) m,网位调整幅度为(11.52±7.09) m。网位与磷虾集群质量中心深度偏离(6.33±3.58) m。(2)网次渔获量为(16.25±6.77) t,拖曳过程中网口始终对准磷虾集群质量中心进入网口的磷虾总量为(27.06±10.19) t,捕捞效率为(63±19)%。(3)网位与磷虾集群质量中心深度差值对捕捞效率影响极显著(P<0.001),两者吻合较好时捕捞效率高;拖速与捕捞效率呈显著相关关系(P<0.05),拖速增大网位上升,捕捞效率越低;曳纲长度增加网位下降,但曳纲长度变化与捕捞效率相关性不明显(P=0.087)。研究结果将有助于南极磷虾拖网作业中有效利用磷虾行为特征,改善网具性能,提高拖网捕捞效率。

Effects of trawling operation parameters on the fishing efficiency of Antarctic krill

To understand the effects of fishing and factors influencing the Antarctic krill (Euphausia superba) trawl operations, operation parameters, net depth, acoustic data, and other information were collected by the krill trawler "Long Teng" of the China National Fisheries Corp., Ltd. fishing in the Southern Ocean from December 2017 to June 2018. The mass center depth and expected catches in the net of the Antarctic krill swarm were obtained by an acoustic method, and the fishing efficiency was quantified based on the net position and fishing log. Then, the GAM statistical model was used to analyze the degree of deviation between the net position and mass center of the krill swarm under different towing speeds and warp lengths to study the fishing efficiency of the net. The results showed that:(1) The depth of the krill swarm mass center was (37.29±9.72) m, the depth of the net position during stable towing of the trawl was (30.72±10.41) m, the adjustment range of the net position was (11.52±7.09) m. The deviation between the net position and the mass center depth of the krill swarm was (6.33±3.58) m. (2) The catch per haul was (16.25±6.77) t, the total amount of krill entering the net mouth when the net mouth was always aligned with the krill swarm mass center during the towing process was (27.06±10.19) t, and the fishing efficiency was (63±19)%. (3) The depth difference between the net position and the mass center of the krill swarm had an extremely significant influence on fishing efficiency (P<0.001), and when the two were in good agreement, the fishing efficiency was high. The net position went up with the increase in the towing speed and a significant correlation was found between towing speed and fishing efficiency (P<0.05). The net position went down with the increase of the warp length, but there is no significant correlation between the change in the warp length and fishing efficiency (P=0.087). The results of this study will contribute to the effective use of krill behavior in Antarctic krill trawling operations, the improvement of net performance, and improvement of trawling efficiency.