The Firefly Squid is a bioluminescent squid growing to a length of only three inches. The squid is equipped with special light-producing organs called photophores that emit a deep blue light. Large photophores can be found on the tips of the tentacles as well as around the eyes. Thousands of tiny photophores can be found throughout the squid's body, giving it the ability to emit light along its entire form. In the Toyama Bay, in the central Japan Sea, the squid are found in fantastic abundance. Normally living at 1200 feet underwater, waves in the Toyama bay pushes the squid to the surface in massive numbers where they are fished by tons from March to June.

The spawning season of the firefly squid also runs during the same period. Millions of squid come together to fertilize and to drop their eggs in the Toyama Bay. The big reunion of these squids is one big light show that you can admire and it attracts thousands of tourists. This event is very important for other sea creatures and sea birds who enjoy eating the dead bodies of the firefly squid. Firefly squids is also considered a delicacy in Japan.

Early in the morning, after 3 AM, sightseeing boats depart the Namerikawa fishing port (Namerikawa is also home to the world's only museum dedicated to the firefly squid) in Toyama prefecture, making a short journey to fixed nets located about 1 to 2 km offshore. As the fishermen haul in their nets, the light emitted by the firefly squid causes the sea surface to glow a cobalt blue, evoking squeals of delight from the tourists.

The lights from thousands of firefly squid can flash in unison or alternated in an endless number of animated patterns. These light shows are thought to serve several functions. They can be used to communicate with potential mates or rivals. They may also be used to disguise the squid's shape and confuse predators, allowing it to escape. On the other hand, it is believed that the squid can also use their blue lights to attract prey. By flashing the lights on and off, they can attract small fish and then pounce on them with their powerful tentacles

Sources: 1, 2

Also see: Bioluminescence in Gippsland Lakes, Australia