INALHAVEN, Me., May 24 — Never before in Maine's long memory has there been a lobster boom like this one.

Year after year lately, the state's lobster landings have risen to record heights, even as the levels of many fish stocks remain miserably low. The latest figures, issued this spring, put last year's catch at an unheard-of 56.7 million pounds, about 20 million pounds above the 100-year average and nearly triple the take of 15 years ago.

"We keep saying, `It can't go any higher than this,' and the next year, darned if it doesn't go up another million pounds," said Pat White, executive director of the Maine Lobstermen's Association.

Something is going very right, and nobody claims to know for sure what it is.

What is clear, though, is that these are exceptionally flush times for the Maine lobsterman, that crusty old rubber-booted, oilskin-suited icon of the state. More than ever, Maine's brooding, pine-pointed, rock-rounded coast is dotted by the bright confetti of orange and yellow and chartreuse lobster buoys, more than two million in all.

Here on Vinalhaven Island, home to 1,200 year-round souls in the heart of lobster country, many a shiny new pickup truck plies the roads, and many a bright new workhorse boat plies the harbor. Island schoolchildren are likelier these days to sport the latest L. L. Bean fashions. And they can know that their lobstering parents are not only better-to-do but even a little hip: a new "Bachelor Lobstermen of Maine" calendar sold out within days last year.

Virtually everyone, from biologists to old-time fishermen, expects the catches to drop again. But for now, Maine lobstermen are enjoying that rarest of modern maritime tales: a fisheries success story.

"The lobster is perhaps one of the only species that's been intensively fished for 150 years and is doing better today than ever," said one lobster expert, Bob Steneck, a professor of marine sciences at the University of Maine.

Which raises an urgent question: How to keep it that way? The answer from a veteran Vinalhaven lobsterman like Walter Day is simple: Just let us do what we've been doing, and otherwise let us alone.

On a typical daily fishing trip one recent dawn, Mr. Day demonstrated. Of all the orange-and-green mottled tail-snapping beauties in his traps — and their numbers are still small this early in the season — only one in every 8 or 10 was kept by him.

Most were "shorts," too small. Some were "eggers," females carrying masses of roe on their underbellies; these Mr. Day marked by cutting a small V-shaped notch in their tails, so other lobstermen would know they were breeding stock and by state law must be thrown back. Others already bore the V-notch.

Oversize lobsters must be relinquished as well, because they are considered superstuds of the ocean that produce bumper crops of young.

It might seem frustrating to throw so much back, but Mr. Day was unperturbed.

"They'll grow up, and I'll catch them someday," he said of the shorts, "if I live long enough."

Or perhaps another Day will. Mr. Day's grandfather lobstered, and his father still does. His son is a lobsterman, his wife lobsters some, and his 5-year-old grandson already has a few traps of his own.

Self-policing like Mr. Day's is the norm in Maine, and many believe it is an important cause of the current bounty. The V-notching, in particular, is technically voluntary in state waters, but virtually all the nearly 6,000 lobstermen in Maine do it, and it is catching on elsewhere as well.

Tight lobstering communities like Vinalhaven also conserve the lobsters in other, social ways. They do not tolerate the kind of cheating often reported before the big lobster crash that hit early last century, when many lobstermen caught and kept illegal lobsters and even scraped the roe off females so they could sell eggers.

Veteran lobstermen also have a convincing way of discouraging outsiders from lobstering in their territory, and require apprenticeships of locals. Some areas of the Maine coast are closed to new lobstermen altogether. State law limits lobstermen to 800 traps each, and summer Sundays are considered no-fishing days.

Another oft-cited possible factor in today's lobster bounty is the complex dynamic of the ocean itself. It appears that over the last 20 years, "the entire western North Atlantic underwent some change in oceanography that influenced, probably, the delivery of the lobster larvae to their nursery habitat," Professor Steneck said. Possibly, some say, the warmer currents that have been observed are more hospitable to the larvae.

Others postulate that the steep decline of predatory fish like cod has allowed more baby lobsters to survive. Still others point out that improvements in gear and technology make lobstermen more efficient.

Another theory, said Carl J. Wilson, the state's chief lobster biologist, is that lobsters may be thriving because they are effectively being farmed. With more baited traps than ever, many a young lobster can stop in to a trap for a snack, then leave through the vents designed to let undersize lobsters escape.

"There are a lot of theories out there," Mr. Wilson said, "and the reality is that we don't know what it is." The boom is "a scientific mystery," he said, and while each theory appears to have flaws, the answer may be a combination of all the theories together.

Lobstering, he and others noted, naturally lends itself to careful conservation. Lobstermen can make individual decisions about each lobster and throw back each reject alive. Fish caught in great nets, on the other hand, are often brought up dead, so that throwing back any illegal catches does little good. Lobster traps do not damage the environment as dragging does, either.

But for all the lobster fishery's pluses, pessimistic voices predominate among the scientists who study it. They see signs that the numbers of young are dropping. Lobster has officially been considered overfished for a couple of decades, and at some point the lobstermen may have to pay. All this alone is enough to worry state officials, even if Maine escapes the kind of vast die-off that decimated the Long Island lobster industry in 1999. (The cause is still unknown.)

The prospect of a sharp drop in lobster landings is particularly worrisome because lobstering has absorbed many fishermen from other, faltering fisheries; even Linda Greenlaw, the swordfish boat captain depicted in "The Perfect Storm," has switched to lobstering. Further, many lobstermen have gone precariously into debt for new boats and equipment.

"Lobster has provided an incredibly good safety net," said George D. Lapointe, the state's commissioner of marine resources. "Everybody asks, `Can we keep a 60-million-pound fishery forever?' No."

Maine is working with other Atlantic states to bolster lobster stocks, and the plan that emerges is expected to emphasize V-notching, limiting entry to new lobstermen and similar measures. Fishermen like Mr. Day say they worry that regulators will impose even stricter measures, like further limiting the number of traps each lobsterman can use, that would make an arduous living all the harder. Better, he said, to let the fishery follow an up-and-down cycle, and drive out the unfit or uncommitted.

"I'm not one bit scared it if does crash," he said. "It will get a lot of people with a gold-rush mentality out, and the real fishermen will still be here with lobster to sell, and we'll all make a living like we always have."

The living lately has been sweeter than usual, of course. Word floats around the docks of especially successful lobstermen who gross $250,000 a year, and take home plenty even after subtracting the usual 20 percent for a stern man to help out and thousands more for bait, fuel, taxes and gear.

The prices the lobstermen command have not dropped as their output has grown. They are getting about $4.50 a pound right now, with lobster still seasonally scarce. The price could drop to $3 a pound in the midsummer peak season, but it never gets much lower, experts say: demand has been growing around the country and the world. Good economic times have helped, some say, along with efforts by Maine to promote its lobsters more broadly.

For all the ringing cash registers, though, this is no dot-com boom. Vinalhaven lobstermen are not exactly buying BMW's, noted Norah Warren, manager of the lobster co-op that markets their catch.

"They might have a new truck, they might have a new boat, their wives might have their kitchen redone, more people go on vacation," Ms. Warren said, "but there's not a lot of showing off about any of it."

The boom, she said, has allowed her and her lobsterman husband to begin contributing to their first 401(k) plan.

A lobsterman-in-his-blood like Mr. Day would fish no matter what, anyway.

"You get your first pair of rubber boots when you're 4 or 5," he said, "and your mother's lucky if she can pry them off you to get you to bed."

Still, the good catches have meant not only a new boat for him and his wife, Lois, who are both 50, but also a house of their own, the first in all their years together.

"If it weren't for the boom, we probably wouldn't have gotten it as soon as we did," Mrs. Day said. "If you call 20 years `soon.' "