Size-specific spatiotemporal dynamics of bigeye tuna (Thunnus obesus) caught by the longline fishery in the eastern Pacific Ocean

Abstract This study aimed to understand the size-specific spatiotemporal dynamics of bigeye tuna (Thunnus obesus) in the eastern Pacific Ocean from 1991 to 2017. A spatiotemporal delta-generalized linear mixed model was applied to catch rate data by size class collected from a Japanese longline fishery. The results showed that the density of bigeye tuna varied spatially across the eastern Pacific Ocean, with spatial segregation by size. The mean predicted density by size in the study area (100–150 °W, 10 °S–10 °N) indicated that adult fish (fork length (FL) > 152 cm) were mainly distributed in the middle of this study area, 110–140 °W in both hemispheres. For the intermediate size stage (FL > 115 to