Relationship between sinking performance of light falling-net and catch rate of Sthenoteuthis oualaniensis

Based on 68 sets of fishing data by light falling-net vessels in the South China Sea from 2013 to 2016, we analyzed the relationship between the sinking performance and catch rate of Sthenoteuthis oualaniensis by generalized additive model (GAM) and Logistic regression model. The results show that the range of the maximum sinking depth (D) and average sinking speed (S) were 53.53–103.10 m and 0.188–0.421 m·s^–1, respectively. The maximum sinking depth and average sinking speed varied significantly in different years (P<0.05), and these indicators in 2015 and 2016 were significantly higher than those in 2013 and 2014. GAM model and Logistic regression model show that the catch rate and successful fishing rate were related to the maximum sinking depth significantly (P<0.1), but were not related to the average sinking speed significantly (P>0.1). The catch rate increased with the maximum sinking depth in general. In order to reach 80% rate of successful fishing, it is suggested that the maximum sinking depth should be increased to 90 m or more.