Migration route of Pacific saury Cololabis saira inferred from the otolith hyaline zone

In order to establish the migration route of Pacific saury Cololabis saira, we measured the radius of otolith annual rings (ROA) in fish collected from areas off the Japanese coast up to 165W in June and July (pre-fishing season) and from fishing grounds in August–November (fishing season). The average ROA for six sea areas that each spanned 10 of longitude sampled during the pre-fishing season were compared with data obtained during each month of the fishing season. The average ROA decreased from west to east and also decreased monthly from August to November. The average ROA of fish caught after October at the peak of the fishing season was equivalent to that of the fish caught in the areas east of 160E or 170E. We conclude that Pacific saury caught by Japanese fishing vessels during the peak of the fishing season migrate from an area east of 160E.