Abstract: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/km2) 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•km2). 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.
