Changes in Distribution Pattern and Condition Coefficient of the Juvenile Japanese Sea Bass with the Chikugo River Ascending

Abstract

The changes in the distribution pattern and the condition coefficient with the ascending progress of the juvenile Japanese sea bass were examined. In the Chikugo River estuary of Ariake Bay, surface towing by a larva net was performed from March to April. A total of 5314 postlarvae and juveniles (SL, 9.5-26.0 mm) were collected by 183 tows. The body depth ratio and condition coefficient increased in proportion to the growth up to 20 mm length. As the research proceeded, the mode of the distribution moved from higher to lower salinity. The concept of distance was introduced to the temporal changes in catch of the sea bass and salinity. In mid March, sea basses were mainly distributed in the sea water area. In mid April, half the number had already reached the fresh water area, and they had condition coefficient remarkably increased. Sudden change in catch when the tide is at turn, and more catch during rising than ebbing tide were observed. Preliminary notes on the ascending mechanism of the sea basses were given. © 1982, The Japanese Society of Fisheries Science. All rights reserved.