1988 年 54 巻 2 号 p. 209-214
In the present paper, the author tried to clarify the arrival property and the composition of a school using the daily growth rings of Japanese anchovy larvae Engraulis japonica in field-collected samples. As a result, the relationship between the number of the daily growth rings (N) and total length (L) of anchovy larvae was shown as the following regression line. N=1.64L-12.94
Daily abundance by the hatching day of Japanese anchovy larvae was appeared in large quantities with a periodicity of 3.8 days.
The daily ages (the days elapsed after hatching) of one large school were in the range of 18 to 62 days with an average of 37 days. The daily age arriving first in the Shirasu fishery ground was 18 days on the average and the earliest age was 12 days. The abundance of anchovy larvae of 20 to 24 daily ages showed a highest frequency at the beginning of August. From this time, this abundance showed the tendency to decrease until the end of September.
Comparing the growth of two larvae schools of anchovy larvae of 25-29 daily ages early in August, total length of anchovy larvae belonging to the school of average 27.1 mm total length was 1.8 mm longer than that belonging to the school of average 37.1 mm total length. This difference was significant (t-test, 0.001 <p<0.01).