Changes in size, water content and C/N ratio were examined on young Nibea albiflora distributed in the Ariake Sound to elucidate their growth and body condition which might decide the success of recruitment. The specimens were collected from the head of the Ariake Sound and the mouth area of rivers which drain to the sound. The youngs occurred twice a year, in June and August. The cohort occurring early grew fast attaining about 150mm in standard length by the end of the year, whereas the other was as small as 60-70mm. The C/N ratio decreased initially with growth, and increased afterward in fall, and the water content decreased consistently. The early changes were thought to be characteristic of young stages and the ones in fall due to the accumulation of energy to overwinter. The body component analysis revealed that the cohort occurring early stores enough energy in fall facing the first winter, whereas the other fails to do that, probably due to food scarcity in the habitat. Local populations of young N. albiflora having different growing conditions were found to exist in the sound.