Standardized CPUE Indices for Neon Flying Squid Using Chinese Squid-Jigging Fishery Data from 2005 to 2025

This study updated the Chinese squid-jigging fishery data for neon flying squid from 2005 to 2025 and standardized CPUE separately for the winter–spring and autumn cohorts. Generalized additive models (GAM), random forest (RF), and gradient boosting machines (GBM) were fitted, and annual standardized CPUE indices were extracted using an expanded-grid approach. A Tweedie-GAM was also applied to evaluate the effects of zero-catch treatment and CPUE distributional assumptions on the standardization results. The standardized CPUE indices produced by the three methods showed highly consistent interannual trends across cohorts, with high pairwise Pearson correlations. CPUE for the winter–spring cohort was relatively high during 2005–2007, declined markedly in 2008, and subsequently remained at a relatively low level with minor fluctuations. CPUE for the autumn cohort increased markedly after 2017, reached relatively high levels in 2019–2020, subsequently declined, and showed a clear recovery in 2025. The Tweedie-GAM and the original GAM produced similar major interannual trends, indicating that the standardization results were generally robust. The updated annual indices provide basic information for subsequent stock assessment and fisheries management of neon flying squid.