"Captain" Tsurizao Morita, a former tuna fisherman, works in his fish shop by day and become the leader of the rock-band Gyoko (meaning fishing port) at night to promote the fish industry and convince his fellow Japanese countrymen & women to eat more fish. All their songs are about fish. During concerts he wield a big fisherman's knife, slicing real fish that they serve afterward to the public.
An old article on Detour Japan gives us more details on the band native of Urayasu in the Tokyo Bay. The band has its own website and has released several CDs, two of them available on Apple's iTunes store (one self-titled album, Gyoko, offering twelve songs for only $1.99 US and the other, Fish & Peace, available for $11.88 US). They even have videoclips on YouTube! Here's their song “Maguro” (Tuna):
There's also a weird promo clip, a news report and an extract from a Spanish documentary...
Japanese rock bands will never cease to amaze me. If they are still rocking around, someone should invite them to an anime convention!