南海鸢乌贼(Sthenoteuthis oualaniensis)资源评估的新方法

为了解南海鸢乌贼(Sthenototeuthis oualaniensis)资源量与分布状况,本研究利用建立在灯光罩网船上的北斗星通渔业信息采集网络,搜集南海鸢乌贼生产数据,并根据灯光罩网作业特点,创建了光诱资源量评估模型,使用克里金插值法,绘制出南海鸢乌贼的分布密度图,估计其总资源量和年可捕量。研究结果表明,鸢乌贼在南海有着广泛的分布,以110.5°–111.5°E、11°–12°N之间的海域和115.5°–116.5°E、9.5°–11.5°N之间的海域资源密度最高,在4 t/km2以上;以112°–112.5°E、14.5°–15°N之间的海域和113°–115°E、15°–16.5°N之间的海域单位努力量渔获量(CPUE)最高,达1 kg/(kW·d·km2)以上。根据克里金插值法估算,在南海108°–118°E、9°–20°N之间的359个渔区,鸢乌贼资源量为204.94万t,总可捕量为99.40万t。评估认为,南海鸢乌贼资源开发潜力大,是未来南沙渔业开发的主要种类。

A New Method to Assess the Population of Sthenoteuthis oualaniensis in South China Sea

In this study we evaluated the biomass and distribution of Sthenoteuthis oualaniensis in South China Sea based on the data collected by Bdstar Navigation fishery information collection network that was mounted on the light falling net vessels. Considering the operation process of the light falling vessel, we built a light fishing stock assessment model and introduced a probability function to calculate the sweeping area and the biomass of S. oualaniensis. We then used kriging method to predict the density of S. oualaniensis and the CPUE. We subsequently generated a map of the distribution of S. oualaniensis and estimated the total biomass and the allowable catch. Our analysis showed that S. oualaniensis were widely distributed in South China Sea with high density（4 t/km^2） in the area of 110.5°–111.5°E, 11°–12°N and 115.5°–116.5°E, 9.5°–11.5°N; in the area of 112°–112.5°E, 14.5°–15°N and 113°–115°E, 15°–16.5°N, the value of CPUE was as high as 1 kg/（kW·d·km^2）. The results of Kriging interpolation suggested that in the area of 108°–118°E, 9°–20°N there was a biomass of 2.05 million tons and an allowable catch of 994,000 tons in 359 fishing areas. The annual allowable catch could be 392,000 tons in 105 fishing areas inferred from CPUE. We assessed that there were 630,700 tons of S. oualaniensis in the area of Nansha Islands and it could be one of the future target species in the deep-sea fisheries. Here we only provided a crude estimate because all the parameters in our model were obtained by the sample vessels. To make an accurate estimate, further investigation will be needed on fishing vessels and fishing ground. It was found that the enhanced machine and light power did not necessarily increase the fishing efficiency. Although a higher light power could enlarge the illuminated area, davits could not support a larger falling net. Moreover, our model could also be used to assess the light arrangement, practice distance, and cost effectiveness in light fisheries.