The study of the swimming behaviour of the flounder larvae Paralichtys olivaceus (TL 9.0-12.0mm) was continued. The time, using a small circulation channel of which the major axis was about 30cm. The channel equipped with a blower to make a wind generated current and the current velocity was regulated to be about 10cm/s by adjusting the blow. Water temperature was fixed at 20°C and salinity at 34‰.
Swimming speed was measured on the difference of circulation time in the channel between that in the state of rheotaxis and that in the state of anaethetization.
Changing pattern of swimming speed for ten minutes was examined using ten individual larvae. The minimum average swimming speed was 1.0cm/s in the first minute and decreased rapidly to almost be 0cm/s in the next four minutes.
Long term changing pattern was observed for sixty minutes using six larvae. The average swimming speed through sixty minutes was 0.91cm/s and 0.86 times (cm/cm) of total length. Larval swimming stamina of flounder seems to be weak much less than that of adult fish of other species.