An investigation has been made regarding the occurrence, and the so-called mass stranding in particular, of the porcupine puffer,
Diodon holacanthus LINNAEUS, in the Tsushima Current region of the Japan Archipelago. The Diodontid fish has been found distributed all over the surrounding waters of Japan, but to be rather rare in Hokkaido and off the Pacific coasts of northern Honshu. The mass stranding is observed to occur commonly and most prominently along the west coasts of Honshu and northern Kyushu during the period from winter to early spring. The season . of occurrence of the stranding is early in the northern districts and is delayed gradually as one proceeds southwards. Along the Pacific coasts of the Japanese Islands, on the other hand, the mass stranding is only sporadically recorded. Shoals of the porcupine puffer other than those which strand themselves on the aforementioned Japan Sea coasts may also make their appearance during the summertime in waters adjacent to Kyushu and the Tsugaru Straits.
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