Catch per unit effort (CPUE) is widely utilized as an index of stock abundance in fisheries assessments, but its interpretation is often complicated by temporal and spatial variation in fishing activity. For this reason, CPUE standardization is essentially needed to produce indices that better reflect the actual stock status. In Korea, however, the limited availability of detailed operational data has posed challenges for effective CPUE standardization. In this study, CPUE data for sailfin sandfish (Arctoscopus japonicus) caught by the East Sea mid-sized Danish seine fishery were standardized using records from the Korean Fishery Radio Station (FRS) from 2004 to 2024. The dataset mainly consists of fishing dates, locations (30’ × 30’ latitude-longitude grids), and catch weights. A generalized linear model (GLM) was applied, incorporating year, quarter, area, and their interactions as explanatory variables. Among these, the year was identified as the most influential factor, followed by quarter and area. The standardized CPUE showed a more stable trend than the nominal CPUE, which showed an increase from 2004 to 2017 and a sharp decline thereafter. This suggests that the standardized CPUE more accurately reflects the underlying dynamics of sailfin sandfish stock abundance. Despite the absence of detailed logbook records, the FRS records effectively captured the spatial distribution of fishing activity and operational patterns, demonstrating their potential as alternative data sources for CPUE standardization. Nevertheless, limitations remain due to the self-reported nature of the data, which may lead to low coverage and potential reliability issues. Improvements in both the quantity and quality of data collection and reporting are necessary to enhance the utility of such data in stock assessments. This study highlights the potential and challenges of using FRS data for CPUE standardization and provides practical guidance for its application in fisheries management.

Introduction
Materials and Methods
    Data
    Target fishery
    Catch trends and fishing characteristics
    CPUE standardization
Results
    Catch trends
    Fishing characteristics
    Spatial and temporal distribution of effort and CPUE
    Analysis of the relationship between explanatoryvariables and CPUE
    CPUE standardization
Discussion
Acknowledgements
References

• Na-Young JUNG(Researcher, Coastal Water Fisheries Resources Research Division, National Institute of Fisheries Science, Busan 46083, Republic of Korea)
• Sung-Il LEE(Professor, Division of Marine Production System Management, Pukyong National University, Busan 48513, Republic of Korea) Corresponding author