サンマの卵,仔稚魚の打上げ斃死

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Every cold season the fish and other organisms are stranded upon some beaches along the Tsushima Current. Of these, the egg and larva of Pacific saury, Cololabis saira (Brevoort), are ones of the most numerous forms. To make clear the destruction of this fish by stranding, the authors observed the phenomenon every morning in the seasons of 1964-1967 at the beach (1.5km length) of Shingu, northern Kyushu (Fig. 1). The results obtained are as follows: (1) The eggs of Pacific saury were found from the end of November to the end of January (Fig. 2), and the larvae, from the beginning of December to the end of March (Fig. 7). These eggs and larvae were supposed to have been originated from the southward migrating fish in our waters. (2) Besides on the some floating Sargassum, the main spawning bed of the fish (Fig. 3 and 4), the eggs were found being attached on the materials from the land (Table 1). They were considered to have been spawned in the inshore waters, which was also supported by the evidence in the developmental stages of the collected eggs (Fig. 5). (3) In the highest peak the number of stranded eggs was estimated to amount to 15 millions a day, and that of larvae to over 1, 000 individuals. These were recorded distinctively just after the prevailing northwester and cold (Fig. 6 and 10). (4) The stranded fish range from 6 to 87mm in total length, accounting the larvae less than 20mm for over 90% of all fish (Fig. 8 and 9). The natural mortality of the fish caused by this phenomenon occur in both the egg and the larva stages mainly less than 20mm. (5) This phenomenon was recognized on the beaches along the Tsushima Current in the spawning season of the southward migrating population (Fig. 1). It may be, hence, considered that the offsprings of the southward migrating population are sometimes destroyed in enormous quantities by this phenomenon in our waters.
社団法人日本水産学会の論文

サンマの卵,仔稚魚の打上げ斃死

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