The Giant Black Catfish that Shook Japan

After the catastrophic Ansei Earthquake struck the city of Edo, Japan in 1855 a new type of color woodblock print known as namazu-e  became popular among the residents of the shaken city. These prints featured giant catfish (namazu) who, in Japanese mythology, caused earthquakes by thrashing about in their underground lairs.
The origin of the story may derive from the notion that catfish can sense the small tremors that happen before many earthquakes and are more active at such times. This sudden pre- earthquake activity may have led to the belief that the catfish were causing the quakes.

Namazu and the kaname-ishi rock

The 1855 earthquake acted as a catalyst for growing dissent about Japan's government. The namazu-e were a cheap, disposable tool through which common people could express their displeasure subversively. 
The government responded with intimidation, including briefly jailing nine guild officials. All namazu-e printing blocks were destroyed on the fourteenth day after the earthquake. The namazu-e had been in production for just two months and only a handful of these prints remain.

More prints here
via  Curious History

This related article on the catfish prints is interesting reading.