Locations of early fishing grounds of saury in the northwestern Pacific

In the north-western Pacific, we found that locations of early fishing grounds of Pacific saury, Cololabis saira, are affected by two factors, the size composition and the meridional shift of the offshore Oyashio Front (OOF). Early fishing grounds are formed nearshore from the central Kuril Islands to Hokkaido in northward OOF years. In southward OOF years, they are far from the coasts. There also exists a tendency that early fishing grounds are formed south-westward (north-eastward) in years when a large (medium or small) size class of saury is dominant and when the OOF shifts north (south). These results support the hypothesis that saury migration is considerably influenced by oceanographic conditions, and that a large size class of saury leads to migration that can reach the vicinity of Japan early in the fishing season.