A fishing boat TROLLING is not a burdened vessell, it still owes a sailboat under sail the right of way. A trawler is, as is a para-sail boat "Restricted in it's ability to maneuver" Ram. If it is a large vessel it would probably be "constricted by draft"CBD also.
Your fisherman had no rights according to the Coast Guard.
I've had the same thing happen numerous times, including getting yelled at in the Ches. Bay for sailing through a guys chum slick,not even near his lines.He was real irate, I had a flare at the ready just in case.
I fish alot and have more problems 100 fold with other fisherman than with sailors.
Next time pull your knife and cut his line and tell him you just saved him a rod and reel.

"I said, now, I said ,pay attention boy!"

The cure for anything is salt water - sweat, tears, or the sea
Isak Dinesen
If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most.
E. B. White