But there is now “a general feeling that protecting the environment means saving jobs,” he said. “There’s a slow realization by government that there are more stakeholders to the sea, which is a public resource, especially with the rapid decline of fishing in the Clyde in the last 25 years. Now in the Clyde they’re not really catching fish anymore, just prawns, scallops and razor clams.”

These days, Mr. Wood said, “I tell fishermen that what we’re doing is for their future, for the future of the fishing industry.”

In 2003, the Woods finally sold the garden center, “and my wife went back to her profession,” social work, helping the elderly repair and adapt their homes, “while I persevered in making no money and saving the world and all that sort of crap,” Mr. Wood said.

His wife recently retired, he said, and the couple’s two grown children are doing well. Martin, 28, works as an instructor in a marine activity center on Arran, teaching children sailing and kayaking, and said he considered himself “incredibly lucky to have found a job here.” Jennifer, 24, is a police dispatcher and coordinator in Edinburgh.

Holy Isle is the southern border of the no-take zone, just across the bay from Lamlash. Andy McNamara, leading a group of young kayakers near the shore, called Mr. Wood “a local celebrity,” then asked him, “So when are you going to the palace?”

Mr. Wood grimaced, then tried to gun the boat to douse Mr. McNamara.

Mr. Stewart, the marine scientist, has been surveying marine life inside and outside the no-take zone for years with the help of graduate students like Jenny Stark, 24, a self-described animal-lover from birth who praised Mr. Wood’s tenacity and local knowledge as they worked together to map the seabed. (But then, he also lets her drive the boat.)

THE impact of the no-take zone has been clear, Mr. Stewart said, with two or three times the number of scallops and lobsters now being harvested, and they are significantly bigger and older, too. “So the number of eggs released is that much more, and so more effective,” he said, adding that the catch in the no-take zone was now the equivalent of an unprotected area 10 times the size.