Analysis of effects of environmental factors on Sthenoteuthis oualaniensis based on structural equation model

To understand the relationship between variations in Sthenoteuthis oualaniensis resources and marine environmental factors, we conducted an analysis of monthly variations in S. oualaniensis resources based on the electronic fishing log data from purse seine operations in the South China Sea from 2019 to 2020. Then we examined the impact of marine environmental factors on the spatiotemporal distribution of S. oualaniensis resources by using a structural equation model. The results indicate that the catch per unit effort (CPUE) of purse seine average presented a consistent monthly trend but with significant interannual fluctuations, having higher average CPUE values in 2020 as compared with 2019. The fishing season for S. oualaniensis in the South China Sea is observed in March and April, primarily concentrated within the region between 112°E−117°E and 8°N−12°N, with a tendency for CPUE to shift eastward and northward during the fishing season. On the other hand, the comprehensive impact coefficient of marine environmental factors on the distribution of S. oualaniensis resources was calculated as 0.38, with sea surface salinity and photosynthetically active radiation exhibiting significant loadings of 0.87 and 0.82, respectively, indicating their importance in influencing the distribution of S. oualaniensis resources. The application of a structural equation model offers a quantitative research approach to examine the complex relationship between marine environmental factors and the distribution of S. oualaniensis. The research provides valuable scientific insights for the sustainable utilization and management of S. oualaniensis resource.