GAO stands for Globe, Aqua and Ocean, and sounds like an Oga-native Namahage shout.

[6] Overlooking the Sea of Japan, it keeps and displays over 10,000 marine organisms, including those from Akita Prefecture's abundant marine resources and over 400 species of rare aquatic animals from around the world.

This is the only tank in Japan where they have Japanese sandfish on display all year round.

[8][9] During the New Year’s season, divers dress up as Namahage and feed the fishes in the main tank.

[12] The former Akita Prefectural Aquarium was founded in 1967, and displayed 300 species including Japanese sandfish, Otters, Penguins and White caimans.