Using charts, graphs and an encyclopedic knowledge of sharks, a leading state marine biologist told the Oak Bluffs selectmen this week that the embattled Boston Big Game Fishing Club's Monster Shark tournament is less about drinking beer and killing sharks, and more about providing a rare opportunity to collect vital information for research.

"As a marine biologist, this tournament is one of the most unique opportunities I have to get information about the health of various species of sharks," declared Greg Skomal, a Massachusetts division of marine fisheries biologist and shark expert. "I think you have to ask yourself what the real problem is, and I think what it comes down to is perception. The fact is the tournament is not a detriment to the population of sharks. It is a unique, unique opportunity to study these animals that we do not get anywhere else."

Mr. Skomal's comments came two weeks after board members discussed ending the town's involvement with the three-day tournament, which takes place annually on the third weekend in July and attracts sports fishermen from up and down the East Coast. After hearing from the town harbor master and several members of the business community during the Dec. 27 meeting, selectmen agreed to ask Mr. Skomal to address the scientific aspect of the tournament.

The event has grown exponentially in recent years, and with it so has criticism. Last year in particular the tournament sparked controversy, with residents registering complaints about the boisterous behavior of participants and debating the ethics of shark fishing and the impact on Oak Bluffs harbor.

On Tuesday, Mr. Skomal educated the board about the tournament's benefit to scientific study and dispelled misinformation about the event. In particular, Mr. Skomal reminded the board that the tournament is catch and release, with most sharks let go unharmed. He said that while more than 2,000 sharks were caught last year, only 48 were killed and brought in to be weighed.

"There were 200 boats last year that were logging every fish they caught, which provided us with total catch information," he said. "That gives us the opportunity to go out and get a large amount of samples without having to go and kill them, and that is unique."

Mr. Skomal also said that all of the sharks killed are used afterward, with the meat being donated to charity.

Mr. Skomal, who has compared the tournament to others such as the Martha's Vineyard Striped Bass and Bluefish Derby, asked how it differs from contests that send anglers after troubled species.

"What makes this shark tournament different from a bluefin tuna tournament?" he asked. "The bluefin tuna is a fish that is 20 per cent or less than what it should be in terms of population, but there hasn't been a single letter written about bluefin tuna."

The real issue, Mr. Skomal said, was the tournament's image, which has been tarnished through coverage on the sports cable network ESPN and by the attention-grabbing antics of a few contestants.

"But there is a whole spectrum of people - not just the chest-beating people - who want to brag about catching a fish," he said.

In reality, Mr. Skomal said, the tournament comprises smart, skilled and conscientious fishermen who have helped him and his team collect almost two decades of data. The information has gone into a relative abundance index that charts the health of a variety of shark species.

"That is just a fancy way of saying that we have been able to use 19 years of information to chart their populations," he said. "And if I felt that this tournament or any other tournament was detrimental to populations of sharks, I would go out of my way to stop them. That's how serious I am about sharks and preserving their healthy populations."

Mr. Skomal also praised the efforts tournament organizer Steve James has taken to minimize the number of sharks killed in the tournament. These include the hefty weight limits for each type of shark brought in, and the penalties imposed on boats bringing in sharks that do not meet those limits.

Selectmen had many questions for Mr. Skomal, ranging from concerns about a tagging program used to track sharks, to how much of the shark meat is donated to charity, to the sexual maturity of a porbeagle.

And with each question Mr. Skomal answered, the board's initial distaste for the tournament seemed to weaken.

"I admit that I didn't know a lot about this tournament, and your energy and passion for sharks is contagious," board chairman Gregory Coogan said.

The board has yet to hear directly from Mr. James, although Mr. Coogan said he spoke with him over the phone earlier in the week. The board said it would invite Mr. James to its first meeting in February.

"I think it will be another good opportunity to educate people about the tournament and I think we have seen that it is not just a killing spree," Mr. Coogan said.