Sakanaction (サカナクション) are a Japanese rock/new wave/electropop band from Sapporo formed in 2005. Their music tends to mesh an eclectic mix of different styles making it hard to classify the band under one specific genre.
The band consists of five members: Yamaguchi Ichiro (vocals & guitar), Iwadera Motoharu (guitar), Kusakari Ami (bass), Okazaki Emi (keyboard), and Ejima Keiichi (drums).
To them the fish symbolism reflects their wish to act quickly and lightly, like fish in the sea, without fearing changes in the music scene. Sakanaction = Sakana (which means fish in Japanese) + Action
This is their song 『バッハの旋律を夜に聴いたせいです。』 Bach no Senritsu o Yoru ni Kiita Sei Desu which tranlastes to (Because of listening to Bach melodies at night) which is off of their fifth album DocumentaLy.
You can watch the music video here. It has a really cool Talking Heads/Herbie Hancock vibe to it visually and perhaps even musically, I definitely recommend watching it atleast once.