From the USCG navigation rules page.
http://www.navcen.uscg.gov/mwv/navrules/navrules.htmIf you are a vessel fishing you have the right of way before a sailboat. This applies whether he is under sail or under power (a sailboat underway not using wind power is considered a power boat by regulation.)
By the way you are considered underway as long as you are not anchored or disabled.
Of course if the other guy doesn't know the rules or chooses to ignore you, you'd better give way

Except where Rules 9, 10, and 13 otherwise require:
(a) A power-driven vessel underway shall keep out of the way of:
a vessel not under command;
a vessel restricted in her ability to maneuver;
a vessel engaged in fishing;
a sailing vessel.
(b) A sailing vessel underway shall keep out of the way of:
a vessel not under command;
a vessel restricted in her ability to maneuver;
a vessel engaged in fishing.
(c) A vessel engaged in fishing when underway shall, so far as possible, keep out of the way of:
a vessel not under command;
a vessel restricted in her ability to maneuver