To clarify the relationship between multi-layer current conditions and damage to set net fisheries caused by Kyucho events, the current velocities at two layers (10 and 30 m depth) were measured in 2015 and 2016 at four stations off the coast of the Tango Peninsula. Our results showed that the mean current speed at 10 m was faster than that at 30 m at all of the stations. In addition, the Kyucho events occurred on more days at 10 m than at 30 m. However, three out of seven cases of the Kyucho damage were caused by strong flows at 30 m only, while the damage induced by a strong flow at 10 m was only one case. In addition, the maximum current speed at 30 m was faster than that at 10 m in five cases. This indicates the importance of the current monitoring not only at 10 m but also at 30 m to understand and reduce the Kyucho damages. The difference of characteristics of the multi-layer current conditions was recognized among the fishery grounds. The improvement of accuracy of the Kyucho warnings can be expected by monitoring the multi-layer current predictions based on this difference.

Chub mackerel Scomber japonicus is one of the most commercially exploited fish species in the northwestern Pacific. In the present study, the relationships between commercial purse seine fisheries records of chub mackerel catches and oceanographic conditions in the region off Tohoku, northeastern Japan, were examined for years 1995 to 2015. The surface layer temperature and the fishing ground distributions showed vast interannual fluctuations. Sea temperature variations greatly impacted the fishing ground formations of chub mackerel. This was especially evident when the offshore Oyashio front shifted south (north) in spring, resulting in relatively low sea temperatures in the southern region off Sanriku before the fishing season began in spring, which seemingly shifted fishing grounds southward (northward) off Sanriku in summer and autumn. Overall, results from this work highlight that regional oceanographic conditions leading up to the start of the fishing season can provide a good indication of the main chub mackerel fishing grounds.