Abstract
The distribution of the mackerel-larvae, P. tapeinocephalus was studied at the three sections, at the surface, 10m layer and 20m layer around Osumi Islands; The results obtained are as follows:
1) Mackerel-larvae were collected at the three layers (surface, 10m layer, 20m layer) in the fishing ground and the adjacent sea from February to May (1958, '59) and the water temperature was varying 16.3-22.4°C).
2) The total length of the larvae was within 4.8-11.8mm, and the larvae-size frequency showed almost the same figures through each month.
3) As the Table 2 shows, the collection-rate (collection frequency/net drawing frequency×102) showed highest at the 10m layer, and the seasonal change was hardly observed.
The collection-rate in the surface showed high rate in the morning, and it became low in the daytime. And the collection-rate in the 20m layer was somewhat lower than that of 10m layer, and the seasonal change was small.
4) The vertical stability change of the layer from surface to 10m is assumed to have some influences upon the distribution of the larvae in the surface layer.