What is the difference between the Japan Coast Guard (JCG) and Port Radio?

Port radio is a radio station governed as a communication facility under the Ports and Harbors Law, and acts as a liaison providing various information to ships using the ports.
The radio station is run by the local authority where the port is located, with the purpose of efficient port operation and ship safety.
MARTIS (Marine Traffic Information Service) is the JCG radio station providing information on marine traffic and it controls navigation, in areas of heavy traffic, as determined in the Maritime Traffic Safety Law and Port Regulation Law.