MIGRATORY HABITUDE OF THE YOUNG YELLOWTAIL BASED ON TAGGING EXPERIMENTS
1961 Volume 27 Issue 4 Pages 291-295
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1961 Volume 27 Issue 4 Pages 291-295
As far as the adult fish of yellowtail, Seriola quinqueradiata, are concerned, tagging experiments have been successfully conducted to prove a distinct habitude of their migration along the coastal waters off Japan. However, the amount of data previously obtained from tagging the young yellowtail has been insufficient to elucidate their migratory habit. Therefore, the author liberated 160 individuals of the young fish with a tag along the Japan Sea coast of Shimane Prefecture. At the time of liberation in May 1958 and June 1959, they were possibly about two years old with the fork length ranging from 36 to 45cm. (Fig. 1). Analytical studies of the fish recovered by October 1, 1960 revealed the following information.
1) The number of the recovered individuals was 34, constituting 22 per cent of the total released. Among the recovered fish those which stayed in the sea for three to nine months after liberation represented 53 per cent, and those staying out over nine months were 32 per cent (Table 1). Therefore, the present experiments may be said to have produced a richer result than some of previous ones.
2) Assuming that an area within a radius 30 miles from a releasing point belonged to a body of a homogeneous water, most of the recoveries were made in that area (Table 2, Figs. 2 and 3). The fact suggests that the young yellowtail have a rather limited range for their movement.
3) They were recaptured almost throughout the year either in a bay, a shallow water or on a reef within five miles off the shore.
4) Although the migratory habitude seems dependent upon topography of a liberating area, it is interesting to note that those released from the Oki Islands appear to have migrated round the islands once or twice a year in conformity with the coastal currents in the area (Fig. 3).
5) The recovered fish had the body weight ranging from 0.8 to 2.0kg. and the body length up to 50cm. On the basis of a previous study none of them could be regarded as older than three years.
