The federal regulations at 47 CFR § 80.310 impose the following mandatory radio watch:
Federal Regulations wrote:§ 80.310 Watch required by voluntary vessels.
Voluntary vessels not equipped with DSC must maintain a watch on 2182 kHz and on 156.800 MHz (Channel 16) whenever the vessel is underway and the radio is not being used to communicate. Noncommercial vessels, such as recreational boats, may alternatively maintain a watch on 156.450 MHz (Channel 9) in lieu of VHF Channel 16 for call and reply purposes. Voluntary vessels equipped with VHF–DSC equipment must maintain a watch on 2182 kHz and on either 156.525 MHz (Channel 70) or VHF Channel 16 aurally whenever the vessel is underway and the radio is not being used to communicate...
This requirement is intended to create a wide area radio watch on Channel 16 for any DISTRESS calls. However, boats equipped with a DSC radio do NOT need to maintain a radio watch on Channel 16 when they are navigating in a designated GMDSS SEA AREA 1.
What is GMDSS SEA AREA 1
A GMDSS SEA AREA I is an area within the radiotelephone coverage of at least one VHF coast station in which continuous DSC alerting is available as defined by the International Maritime Organization. A GMDSS SEA AREA 1 is an area declared by the Coast Guard of a maritime nation as the distance to seaward from the coastline in which the that Coast Guard is able to maintain a radio watch on DSC and Channel 16. The United States' GMDSS SEA AREA 1 was declared after the USCG RESCUE 21 radio system was constructed, finished, and in service.
The official declaration of the GMDSS SEA AREA 1 for the USA was published in the Federal Register on January 20, 2015:
Federal Register wrote:The Coast Guard defines Sea Area A1 as those areas where more than ninety percent of the area within 20 nautical miles seaward of the territorial baseline along the East, West and Gulf Coasts of the United States, excluding Alaska, and including Hawaii, Puerto Rico, Guam, the Virgin Islands of the United States, and the Northern Mariana Islands of Saipan, Tinian, and Rota, is within coverage of Coast Guard very high frequency (VHF) Coast Stations that provide both a continuous watch for Digital Selective Calling (DSC) distress alerts on Channel 70 and a capability to respond to distress alerts.
The reasoning behind the exemption for individual boats is a boat equipped with a DSC radio is automatically maintaining a radio watch on the DSC channel where a DISTRESS ALERT broadcast would be made by a vessel with a DSC radio.
Note that the defined USA GMDSS SEA AREA 1 does NOT include the Great Lakes, as they are inland waters. This seems to imply that a boat equipped with a VHF radiotelephone operating on the Great Lakes would still be required to maintain a radio watch on Channel 16, even if using a DSC radio, even though the USCG RESCUE 21 radio system coverage includes the Great Lakes to at least 20-miles from shore. I have not found any official interpretation regarding lack of an exemption on the Great Lakes from mandatory monitoring of Channel 16.
In general, keeping a radio watch on Channel 16 is a very good practice. Although Channel-9 has been designated for non-emergency calling, most all boaters continue to make calls to other vessels on Channel 16. And, of course, many boaters like to listen on Channel 16 to "read the mail" about boating activity occurring in radio range of their location.