Mackerels have become to appear earlier in the coastal area of Iwate Prefecture, Sanriku region in recent years, resulting in overlap with the release period of hatchery-bred juvenile chum salmon into wild. Mackerels were suspected to prey on the juvenile chum salmon during their coastal residence. We investigated the predation of mackerels on juvenile chum salmon by angling in Miyako Bay, Iwate Prefecture, during the spring season.