Brief migration of the grass puffer, Takifugu niphobles, to fresh water from salt water

Abstract

The grass puffer, Takifugu niphobles, is a peripheral freshwater fish often seen in brackish water. In the Sai River, Miyazu, Japan, we found that the grass puffer migrate to fresh water from salt water in June and July. Most of the grass puffer stayed in fresh water for 3.6 h on average and returned to the sea during the day. A low salinity tolerance experiment indicated that the grass puffer can live in fresh water for 2 days but not for longer than 4 days. Based on these findings, we discuss the physiological effects and ecological implications of the migration.