At the derby weigh station, curious onlookers are often just as large a group as the fishermen themselves. Friends and family stop by as catches are brought in, and tourists wander down to the docks to watch the happenings. Sometimes, four-legged friends make appearances.

No scraps for Scup today. — Ivy Ashe

On Wednesday morning, filet volunteer and committee member David Hearn brought along his four-year-old black Labrador, a handsome (and hungry) pup with the perfect derby name: Scup.

“He’s been here a few times — in the mornings, when there’s not too many people,” Mr. Hearn said.

Scup followed Mr. Heard to and from the filet storage area, occasionally straining at his leash to bark at a pair of ducks floating in the harbor, but mostly sticking close to his owner’s side.

In the final minutes of morning weigh-in, weighmaster Roy Langley brought two bluefish, one large and one small, out to the filet station, tossing the smaller onto the deck. Scup trotted over to inspect the catch, tentatively licking the scaly blue. Mr. Hearn told Scup to leave it, and the Lab went back to the table, impressing those around with his obedience training.

“He knows what’s coming to him,” Mr. Hearn said. “He just doesn’t want to have to work for it.” And he tossed Scup a scrap.