John Casey with his 24.82-pound striped bass. — Mark Lovewell

At the stroke of 12:01 a.m. Sunday, no one turned into a pumpkin, but a whole lot of people turned into obsessive, superstitious and sometimes secretive competitors in the Martha’s Vineyard Striped Bass and Bluefish Derby.

The first four days of the 70th annual fishing derby were graced with clear, warm weather as anglers were stationed on boats or at their favorite fishing spots. About 2,800 pounds of fish have been weighed in so far, with striped bass leading the pack: 138 bass have been weighed in, 115 caught from boats. Meanwhile, the shore bonito have been scarce; just three have hit the scale so far. The first shore bonito and current grand leader was a 5.64-pound fish weighed in Wednesday morning by Ron McKee.

The derby continues until Oct. 17. Until then, the weigh-in station at derby headquarters at the end of Dock street in Edgartown will be a hub of activity twice a day, from 8 a.m. to 10 a.m. and 8 p.m. to 10 p.m.

Amy Lima with her 19.30-pound shore striped bass caught in the wee hours Sunday. — Courtesy Amy M. Lima

The weigh-in action began Sunday morning when weighmaster Roy Langley slid open the door to derby headquarters, rang his bell, and officially welcomed everyone to the contest. Aidan Gates of Tisbury was first in line. Wearing a maroon fishing windbreaker and a blue shark backpack, the 14-year-old Martha’s Vineyard High School freshman is already a derby veteran. He began competing when he was 10.

Aidan was asked when he caught the gleaming false albacore he was holding.

“About 10 minutes ago,” he said.

When Mr. Langley plopped the fish on the scale, the electronic numbers settled on 5.95 pounds, and Aidan Gates was the leader of the derby. Only for a short time, but the leader nonetheless.

Roy Langley weighs in Mr. Casey's striped bass. — Mark Lovewell

Next in line was Petar Petyoshin of Edgartown, with two gleaming false albacore. “I caught two, both of them the first and second (false albacore) ever,” he said. “Never caught one before.”

Unfortunately for Mr. Petyoshin, his biggest fish fell short of the 25-inch minimum derby size, by a half inch.

Christopher Bonica followed with a hefty bluefish, weighing in at 10.19 pounds.

But it was John Casey who drew the biggest oohs and ahhs from the assembled crowd, with a striped bass more than half as long as Mr. Casey is tall.

First fish of the derby: Aidan Gates and his false albacore. — Mark Lovewell

Mr. Casey was out most of the night Sunday in a boat he and his brothers affectionately call the “tin can.” It’s not a very fancy vessel, but a whole lot of derby fish have been hauled aboard over the years.

He heaved the fish onto the counter, and Mr. Langley slid it onto the scale, where the big bass registered 24.82 pounds. Four days later, Mr. Casey’s name is still on the leaderboard for boat bass, and the fish is still the biggest of the derby.

Amy M. Lima of West Tisbury was briefly the shore grand leader Sunday, with a 19.3-pound striped bass caught in the wee hours. “He took three runs out on me before I landed him,” Ms. Lima said in an email to the Gazette.

But Ms. Lima said the best part of the day was getting a big hug from weigh station volunteer Amy Coffey, and being told she weighed in the first fish caught by a woman during this year’s contest.

A fair crowd of the curious and the faithful were on hand to see the first fish arrive Sunday, including two bleary-eyed children in Crocs and striped pajamas, looking like jailbreakers from a tiny prison.

Ed Jerome, president of the derby committee, wandered by the line of people waiting to weigh in, on his way to a boat bound for his favorite fishing spot. Pointing to a couple of false albacore, he asked in mock amazement, “What are those things?”

“A fish with a lot of spots,” someone replied.

So begins the glory and the heartbreak of a legendary fishing contest on a fish-crazy Island.

Send derby photos to news@mvgazette.com and follow all the action at the Gazette’s derby headquarters, vineyardgazette.com/fishing-derby.