[MHml] radar transponders/ais

[Peter Gelinas]

Re: vessels required to carry AIS

Vessels on international voyages that are:
Self-propelled commercial vessels of 65 feet or more in length, other than 
fishing vessels and passenger vessels.
Tankers.
Passenger vessels that are over 150 gross register tons.
Vessels, other than passenger vessels or tankers, over 300 gross tons.

Vessels operating within U.S. Vessel Traffic Service or a Vessel Movement 
Reporting System area denoted in 33 CFR 161, that are:
Self-propelled commercial vessels of 65 feet or more in length, other than 
fishing vessels and small passenger vessels certificated to carry 150 or 
fewer passengers.
Towing vessels of 26 feet or more in length and more that 600 horsepower.
Passenger vessels, regardless of size, certificated to carry more than 150 
passengers for hire.
The terms herewith are as defined in 46 USC 2101, unless noted in 33 CFR § 
164.46. Note: the term fishing vessels does not include fish processors or 
tender vessels.

WARNING
Some vessels do not carry A.I.S.
It is important at all times to keep
a proper lookout. The A.I.S radar is
not a substitue for good seamanship.

Above is some text copied from the USCG site and the NASA Marine instrument 
site.