ホタルイカと光

摘要

In the early spring, the large group of firefly squids (Watasenia scintillans) surge to theseashore in the Toyama bay. They are thrown out to the seashore by the wave and the tidal stream fre-quently. A lot of firefly squids surge on the pitch-dark seashore, a blue photophore is blinked, and it isvery fantastic to dye the seashore to blue. It is called, "Firefly squid's MINAGE (throwing oneself)" inthe Toyama bay area. These are known for a long time (In Edo period), and are poetic events of theToyama bay of the early spring with the "MIRAGE". The large group of the firefly squid comes toToyama Bay for spawning in spring. They live in 200m-300m depth in daytime and move to the shallowsat night where some of them are caught by the fisherman's set-net. The firefly squid at the spawning timemoves between the seashore and the offshore by the orientation behavior that uses moonlight. However,they mistake the orientation, and approach the seashore taking the wrong course at the new moon. Then,they are thrown out to the seashore by the wave and the tidal stream frequently. The diel vertical migra-tion between the surface and 300 m in depth is initiated by the light intensity decrease in the sea accord-ing to the sunset. The vertical migration is not caused when there is a rainfall. Therefore, the number ofsquids which visits to shallows decreases sharply, and the catch in the set- net decreases. Consequently,the Firefly squid's MINAGE does not occur.