ROCKLAND – Wilderness preservation isn’t just a question for land managers.

During the annual Maine Fisherman’s Forum Thursday, fishermen, scientists, environmentalists and lawmakers tackled the question of how to preserve underwater biodiversity off the state’s coast without destroying a centuries-old fishing tradition.

Underwater preserves known as “marine protected areas” could be the long-term answer, but the idea would have immediate economic consequences and is tremendously controversial.

“It is, for most of us, a political hand grenade,” said George LaPointe, Maine Department of Marine Resources commissioner.

Marine protected areas have been a popular conservation trend since President Bill Clinton signed an executive order shortly before leaving office that defined an MPA as “any area … that has been reserved … to provide lasting protection for the natural and cultural resources within,” and encouraged their development.

President George W. Bush has given his support to the plan, and created a national advisory committee which includes LaPointe and Barbara Stevenson of the Portland Fish Exchange.

However, the MPA definition is extremely broad. Depending on interpretation, it may include everything from temporary closures designed to protect spawning fish to strictly regulated marine sanctuaries where no fishing is allowed. These “no take” zones frighten fishermen, but environmentalists see permanent wilderness as an essential component of a marine conservation plan.

Academically speaking, almost everyone favors MPAs of some sort. Successful preserves have been shown to boost overall biodiversity, protect rare species and even increase harvests for fishermen working near the preserve boundary by serving as a nursery area. Fishermen often support limited closures to protect their resources.

But when shaded spots on a map translate to 10, 20 or more fishermen displaced by a preserve with nowhere else to set their nets or traps, MPAs become a “lightning rod,” LaPointe said.

‘There is a perceived lack of trust all around on this issue,” he said.

The Gulf of Maine already has more than 10,000 square miles in reserve, most of that in seasonal or species-specific management, said Paul Howard, executive director of the New England Fisheries Management Council.

These existing preserves are working, he said, calling the recovery of groundfish over the past decade “remarkable.”

But fisheries science relies on a complex network of different species, whose habits aren’t completely understood. Contradictory data abound.

Robert Steneck, a professor in the University of Maine School of Marine Sciences argued that Maine’s fishing heritage may be at risk because of a decline in marketable species, some of which can be blamed directly on overfishing, though large-scale ecosystem changes and habitat degradation also play an important role.

“I rarely hear any [fishermen] say, ‘Gee, it’s getting better and better every day,'” he said. “The days of big cod and lobster living together are gone. The world has fundamentally changed.”

California has mandated a system of MPAs, many of which bar fishing, but neither the federal government nor the Maine Legislature are considering such a drastic step here. Maine will more likely begin by considering the effects of existing closures, then asking if and where more restrictive MPAs might be appropriate.

“I don’t want a situation where all you have is a hammer so everything looks like nails,” Steneck said.

Several speakers who have been involved with MPAs designed to protect lobster, corals and cod off Nova Scotia shared their experiences.

The goal of an MPA, be it to boost populations of a particular fish or to create untouched underwater wilderness, must be clearly defined, they said.

Without solid goals and the means of measuring progress, fishermen will be tough to convince, and rightly so, they said. But if a well-designed system of MPAs is meeting its goals of improving habitat and biodiversity, preservationists and fishermen alike should ultimately benefit.

“At the end of the day, sustainability is job security for fishers,” said Ken Frank, a fisheries scientist from Nova Scotia.