The coastal shelf in Toyama Bay is small, and the sea floor drops sharply a short distance from the land, with the deepest parts of the bay being more than 1,200 meters deep. Into the surface seawater of the bay, warm-water fish species are carried by the warm Tsushima current, while in the deep seawater at a depth of over 300 meters coldwater fish species live in the much cooler waters of the Japan Sea (deep seawater) at a temperature of around two degrees Celsius. Thus, Toyama Bay has an environment where both warm- and cold-water marine life can exist, and thus it is a treasure trove of marine resources.
Seventy percent of the total fish catch is comprised of migratory warm-water fish such as tuna and yellowtail, while the rest includes many kinds of deep-water fish and shellfish such as sweet shrimp, benizuwai crab, Japanese ivory shell, firefly squid, and white shrimp. Rare firefly squid and white shrimp are particularly valuable marine resources that are rarely found in areas other than Toyama Bay. Every spring, a large number of the tiny squids come to the coast from waters more than 200 meters deep for spawning. The mysterious pale blue light emitted by the squids in the night sea when they are caught is a common spring sight in Toyama Bay.
The habitat of the world-famous glowing firefly squid limits itself to the Western Pacific ocean. The firefly squid is a middle-deep sea squid that can live on depths of 600 to 1200 (365m) feet. The body of these little squids are covered with photophores that give a blue light. The main goal of these photophores is to lure little fishes, so that it can catch them easier. Just as the vampire squid, the firefly squid has its photophores totally under control. He can make different light show patterns with these photophores to communicate with others, to distract a predator or even lure their pray.
The reproduction of the firefly squid, once a year (March to June) millions of squids come together to fertilize and to drop their eggs in the Toyama Bay in Japan. The big reunion of these squids is one big light show that you can admire and it attracts thousands of tourists. Once the firefly squids have done their job, they die. The firefly squid has a one year life-cycle and once that year is over they die and wash up on the shore. This event is very important for other sea creatures and sea birds who enjoy eating the dead bodies of the firefly squid.
Firefly squids are just as many other sea creature a delicacy in Japan and they're mainly caught when the firefly squids come together to mate.
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.
Toyama Bay's firefly squid fishing season opened on March 1 and is expected to continue until the end of June. Sightseeing boats are scheduled to run until May 7.