There was an early morning theft today at derby headquarters: A gull swept down while fillet master Hank Unczur wasn’t looking and stole one of his four bluefish fillets.

It’s only day three of the derby, but the herring gulls have taken up residence at the Edgartown Yacht Club and the newly-built Boathouse restaurant during derby weigh-in. Prematurely ready, the gulls are well-versed as they are in the affairs of the derby. They, too, know when it is derby time.

Mr. Unczur, 82, has been involved with the derby for 20 years as a volunteer. Mondays and Tuesdays are his mornings to volunteer at the weigh station at the foot of Main street. He dresses in the traditional orange wet-weather overall pants and wears a derby hat with the button number 510. It is a lucky number, and it has been his derby number for 15 years.

Mr. Unczur is a talented fillet master. But why would he be filleting when he could be out fishing with the rest of the Island’s talented anglers? “When you are 82 years old, you don’t go out too far,” Mr. Unczur said.

A few fish were weighed in at the Tuesday morning weigh-in. Weigh-in runs from 8 to 10 a.m. every day during the month-long contest. They also run the weigh-in from 8 to 10 p.m. daily.

Every striped bass, bluefish and bonito that is donated gets filleted, and the fish are donated to the Island’s elderly. Nothing goes to waste. Even the fish wracks are given to local fishermen for their use as bait.

Mr. Unczur was focused on the usual routines when the theft occurred.

“I had just finished filleting two bluefish,” Mr. Unczur said.

“I turned around to get a tray for the four fillets.

“When I got back, a fillet was missing,” Mr. Unczur said.

It is difficult to tell which of the birds was to blame. In the early sunshine morning, there was a bright white gull standing at the peak of The Boathouse, looking suspiciously interested. Another was over at the Edgartown Yacht Club roof, looking, suspiciously, deliberately uninterested.