The great white sharks patrolling the world’s oceans, including the shallow waters just off Long Island’s beaches, once more showed their power to fascinate on Saturday when one of their champions, Chris Fischer, drew a standing room only crowd to the Sag Harbor Whaling & Historical Museum.

At least 100 people turned out to hear Mr. Fischer, a charismatic TV producer and host of sport fishing adventure shows, talk about the shark-tagging, tracking and data collection expeditions of his ship M/V Ocearch.

The ship, after a long sharking voyage to Australia and South America, has been working off the beaches of the South Fork since August 11. Mr. Fischer said he believes the waters off Long Island are a prime nursery site for the Atlantic great white shark.

In one week, Ocearch tagged and released nine shark pups near Montauk, said Stephen Lobosco when he introduced Mr. Fischer. Mr. Lobosco, whose mother Barbara is a co-president of the museum, arranged for Mr. Fischer’s visit with museum board member Peter Drakoulias.

Chris Fischer, TV fishing show host and founder of Ocearch, tells a standing-room-only crowd at the Sag Harbor Whaling Museum on Saturday, August 27, about the organization’s effort to tag great white sharks and collect data to prove that they breed in the waters just off Long Island’s beaches. Peter Boody photo

The Ocearch website includes a global shark tracker that allows anyone with a computer to follow scores of sharks all over the world. Last year, the site recorded 13 billion impressions.

The tracker is a result of Mr. Fischer’s discovery that he could achieve spectacular “bandwith” — an even greater viewership than his recreational fishing TV programs — “by inviting everybody” to participate in the Ocearch mission in real time over the internet.

“Suddenly I was like, ‘Oh wow. We have another way toward scale. This is the Google model …monetize the scale, not the product,” he said.

The Ocearch mission is to end the ignorance that cloaks human understanding of great whites and other shark species by tagging them, developing data about their behavior, and widely disseminating it for free. The goal is to stimulate the academic research that ultimately will allow governments to establish policies to protect shark populations.

That’s vitally important, Mr. Fischer explained, because great whites are a “keystone” species that keep the ocean ecosystem in balance. With no great whites, which feed on squid, the squid population would soar and game fish populations would plummet because squid eat their young, he explained.

Without sharks, it would be “a dead ocean,” Mr. Fischer said.