Mr. Fischer chafes at the criticism; he said that he had been trying to shed the image of a reality-TV jock, and that one reason for inviting the news media was to open the process to the public. He dismissed the objections as “emotional rants” by an ill-informed fringe group.

For example, he said, tags implanted on sharks through harpooning are less reliable than those attached to the fin because they can fall off after six months and they emit a signal only if receivers are placed in the water around them. It is impossible to know where the sharks are going, he said, and therefore impossible to plant receivers everywhere they might go. By contrast, he said, when sharks are captured, the GPS tags can be attached securely with a drill. They are read by satellites every time the fin breaks the surface of the water and can emit signals for five years.

Mr. Fischer also said he was working with marine biologists who appreciated the chance to see a great white up close.

Greg Skomal, a shark expert working for the State of Massachusetts, was on the Cape Cod expedition. He has tagged sharks through harpooning, but this was the first time he had his hands on a live one.

“This vessel is one of the only platforms that gives scientists unprecedented access to the great fish,” he said. “Any time you capture a fish by any methodology, you’re going to expose it to some level of stress. But we try to minimize that.”