CPUE standardization of bigeye tuna caught by Korean tuna longline fishery in the Indian Ocean, 1979-2020

In this study the CPUE of bigeye tuna caught by Korean tuna longline fishery in the Indian Ocean was standardized using lognormal constant model and delta lognormal model with added cluster factor as a categorical variable for addressing target changes over time. The data used for the CPUE standardization were catch in number, hooks used, fishing location (5° cell), and vessel identifier by year, quarter, and region. The standardized CPUE for R1S decreased from 1979 to 2010, and after that it has shown an increasing trend. For R2, it also showed a decreasing trend until the early of 2000s, and then it has shown a slight increasing or stable trend. For R3, from 1979 to 1990 it decreased but after that showed a stable trend.