Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
For each region, colors of the prefectures in the map correspond to those used to represent the annual variation in number of releases. Note that no releases have been performed in Hokkaido and the Northern Pacific region.
