Enhanced local recruitment of glass eel Anguilla japonica in Oyodo River, Miyazaki and offshore environmental conditions in 2002
To examine the environmental factors controlling the inshore recruitment dynamics of Anguilla japonica in the Oyodo River, Miyazaki Prefecture, Kyushu, glass eel samplings were carried out using fyke nets during winter (November–March) of 1994–2014. The peak CPUEs (catch per unit effort) were observed between November and February, but differed from year to year. The yearly CPUE was extremely high in 2002, when the sea surface temperature (SST) in the offshore area of the Oyodo River was the lowest in winter of all the sampling years. The negative SST anomaly of less than − 0.5 °C was sustained in the offshore area during the recruitment season in 2002, which was caused by two combined factors; low air temperature and the Kuroshio path. The oceanographic data showed that the dominant path of the Kuroshio was displaced eastward at 31°N in 2002, which was different from the average Kuroshio path. The eastward displacement of the Kuroshio induced a cyclonic mesoscale eddy in the offshore area of the Oyodo River, resulting in the entrainment of the cold seawater into coastal waters from deep water. The oceanographic condition in relation to the continuous low SST could be favorable for local recruitment of glass eels.
KeywordsAnguilla japonica glass eels Low seawater temperature Kuroshio Cyclonic eddy Oyodo River
This research was partly commissioned by the Fisheries Agency of Japan and grants from the Japan Fisheries Research and Education Agency. We are grateful to the Japan Meteorological Agency and Ministry of Land, Infrastructure, Transport and Tourism, Japan for providing the observational data. We used the supercomputer of the Japan Agriculture, Forestry and Fisheries Research Information Technology Center for analyses.
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