抄録
Data on the swimming layer were quoted from the author's previous report, and those on the vertical distribution of water temperature in the areas B and C (Fig. 1) were obtained from the investigations by the “Sagamimaru”, the former research boat of the Kanagawa Prefectural Fisheries Experimental Station, the “Nachimaru”, the research boat of the Wakayama Pref. Fish. Exp. Stat. and the “Iwatemaru”, that of the Iwate Pref. Fish. High School.
Records on the surface water temperature and rate-of-catch of black marlin in area A have been obtained from the investigations by the Kanagawa Pref. Fish. Exp. Stat. and the Nankai Regional Fisheries Research Laboratory.
Data on the vertival distribution of water temperature and rate-of catch of black marlin in the area of Lat. 10°-30°N., Long. 125°-135°E. were quoted from the report by Ueyanagi10).
The variation of swimming layers of yellowfin tuna and big eyed tuna is not concerned with the variation of water temperature. Therefore, it is supposed that the swimming layer of the fish above mentioned would be independent on the water temperature.
The shoal of black marlin distributes mostly in the habitat layer of 24°-25°C., and its swimming layer changes seasonally with the vertical removal of water temperature. But the vertical transition of swimming layer is less than that of water temperature from the reasons when the habitat layer comes up nearer to the surface the shoal swims in most cases in the under layer of 22°-24°C., and when the layer of 24°-25°C. goes down nearer to the bottom the fish remain mostly to the upper layer of 25°-27°C..
The better fishing rate of black marlin would be evaluated if we could estimate its swimming layer from the phenomena above mentioned.
