A variety of fish, but Cod is very common. It has very high concentrations of beneficial oils in the liver.
Japan exports seafood, cars, oil, electronics, and other miscellanious exports. Japan also has a large US Navy base on the Honshu island. In other words, Japan is just a trading post.
Freshwater fish lake trout - masu rainbow trout - nijimasu river trout - ayu koi - carp unagi - eel Saltwater fish, blue tuna - maguro pink, fat belly tuna - toro maguro swordfish - kajiki maguro...
salmon, yellow salmon, tuna, mackeral
Traditionally, Cod was always used in Fish & Chips. Since fish stocks have been depleted, it is more common now to have Haddock.