The captain of a fishing trawler was killed today when a line holding the net being towed behind the boat snapped and struck him in the head off the Plymouth coast, U.S. Coast Guard officials said.

The 40-foot boat out of Plymouth was 10 miles out when the first mate, and the only other person on board, radioed a distress call about 3 p.m., Coast Guard spokesman Petty Officer James Rhodes said.