FRIENDSHIP LONG ISLAND, ME. The sun is setting, an icy wind has picked up off the ocean, and the tide has gone out, leaving the outboard skiff stranded on the shore of this nearly deserted island.

This is the moment that Diane Cowan has awaited. Wearing tall rubber boots, she wades into the shallows, overturning rocks and small boulders, her breath visible in the fading light.

Quick as lightning she grabs at something flapping in the water. "Got one!" she exclaims, before opening her rubbergloved hands to reveal her catch.

Cradled in her hand is a tiny American lobster—a mere four inches long, its antennae flicking with curiosity, its ciaws thrashing about in protest. "Don't worry. I won't hurt you," she says before placing it in a plastic container. Nearby, other tiny juvenile lobsters scrabble or rest in similar dishes until Ms. Cowan can measure and tag them. None is longer than her hand.

A SOARING POPULATION

Until recently. few lobster scientists knew that Maine's rocky tidal shores served as nurseries for large numbers of juvenile lobsters. Now, Ms. Cowan, founder and president of the Lobster Conservancy, a nonprofit research organization in Friendship, Me., is counting, tagging, and tracking the small crustaceans, collecting data that may help scientists better predict trends in Maine's lobster stocks. The information may also solve a mystery about the delectable shellfish that is central to the people who harvest them.

Scientists have been baffled at the steady rise in catches of American, or "Maine" lobsters over the past 15 years, which occurred while they warned of a decline. While increasing fishing pressures destroyed New England's stocks of cod, haddock, halibut, and sea urchins—and more and more fishemen have turned to lobstering—lobster stocks have not only stood up, they appear to have increased.

Last year, Maine's lobster catch soared to yet another record high. despite the fact that Gulf of Maine lobster stocks have been officially classified as overfished for nearly two decades. Maine lobstermen landed 52.3 million pounds of lobster in 1999, compared with 47 million pounds in 1998 and typical catches of 2O million pounds in the half-century ending in 1985. "Every time the scientists say the stock is about to collapse, there has been a groan [of frustration] from the industry," says James A. Wilson. professor of marine science at the University of Maine at Orono. "Clearly, the model they are using is not one that hits the nail on the head."

The approach that has proved so off-target relies on the size and quantity of lobsters landed by fishermen. Such data in recent decades have frightened fishery managers because around 90 percent of lobsters caught in Maine have just reached their legal size limit and are unlikely to have bred. This has led to predictions that the brood stock would fall, taking away the foundations of both the lobster population and a way of life in coastal Maine.

Although nobody knows why lobsters have thrived, experts have floated a few theories. The collapse of cod and other fish stocks in the early 1990's may have reduced the numbers of predators that eat baby lobsters, while increasing the habitat available to lobsters. As another possibility, lobstermen may be inadvertently serving as lobster farmers. The increased number of traps—and bait—in the water may be feeding the young, which are smali enough to slip into and out of traps. And Maine's regulations—which prohibit taking lobsters over a certain size—may have created a big stock of large breeders, hiding somewhere out in the deep and as yet undetected by fisheries managers.

Whatever the reason, scientists say they are finally making some headway in managing lobster resources. New research has pointed to a better way of predicting what the population will do in the future.

Recent studies suggest that the best time to assess the prospects of a given generation of lobsters is when they first settle on the bottom a few weeks after they are hatched, rather than the traditional time— at around 7 years of age, when they reach minimum commercial size.

Lobsters lay eggs by the tens of thousands, which hatch to become tiny larvae that get carried by ocean currents, Fish and other predators eat the vast majority of those larvae. But after 30 to 40 days, the cricket-sized survivors drop to the bottom and search for a place to hide.

"Mortality drops off dramatically once the juveniles find shelter, because they pretty much don't move for the next year or two," says Richard A. Wahle, a research scientist at the Bigelow Laboratory for Ocean Sciences in Boothbay Harbor, Me. Mr. Wahle and his colleagues made this discovery by collecting young lobsters from the ocean floor to monitor their population trends. "You have survival rates of 70 to 90 percent, which was a surprise to all of us.

Such work raised the possibility that by surveying juveniles, scientists might be able to predict more accurately what the ["Wev'e got this reasonably well nailed down, so we should be able to use this as a good indicator of population tendencies."] commercial lobster stock will look like five or six years down the road.

"We've got this reasonably well nailed down, so we should be able to use this as a good indicator of population tendencies," says Robert S. Steneck of the University of Maine's Darling Marine Center, in Walpole.

TRACKING DOWN THE JUVENILES

Mr. Steneck, Mr. Wahle, Ms. Cowan, and other scientists are now tracking the juveniles as they become adolescents, the period of time between when they leave their shelters at age 3 and the time, two to five years later, when they reach the minimum legal carapace length of 3-1/4 inches and start landing in lobster pounds. Mr. Steneck says they're already seeing a "nice correlation" between the number of bottom settlers they've recorded in a given year's "class" and the number of undersized lobsters showing up in lobster traps a few years later. Further confirmation will come from new trawl surveys by the Maine Department of Marine Resources, and data from Ms. Cowan's intertidal surveys.

If there is a correlation between larvae settlement and future lobster landings, the fishery may be in for a downturn. Since 1996, Mr. Wahle and his Bigelow colleague, oceanographer Lewis S. Incze, have seen a drop in the quantity of larvae and newly settled lobsters at two sites in the western Gulf of Maine. If similar trends are occurring at other locations on the coast, the lobster industry might see a decline in the next couple of years.

"The big mystery is why there's this change in larvae and post-larvae," Mr. Incze says. "Is it the transport'? The egg hatching'? The result of overfishing? We have no idea."

Scientists agree that early detection of changing population trends is much easier than figuring out why the changes are occurring. Understanding where the larvae come from—and what conditions improve their survival—is now a focus of research in this direction.

LONG TRIPS ON THE CURRENTS

One theory is that a significant proportion of larvae travel great distances on coastal currents before arriving at nursery grounds.

Last year, larval surveys by Eric Annis, a graduate student at the Darling Marine Center, suggested that the Eastern Maine Coastal Current might act as a larvae superhighway. The current, which flows from east to west down Maine's coast, may deliver huge numbers of larvae into Maine's highly productive Penobscot Bay lobster fishery from as far away as New Brunswick, Canada. "If this proves correct, then, in the big picture, that means how this fishery gets managed by other states and countries is very important," says Mr. Incze, who supervised the research.

Earlier sampling of newly settled iobsters by Mr. Wahle also showed few larvae in eastern Maine (where lobster catches are small) and large quantities in western Penobscot Bay (which has record landings). Mr. Steneck says it's possible that a warm ocean-temperature front off Penobscot Bay may prompt large numbers of larvae to settle to the bottom, creating a veritable snowfall of tiny lobsters.

RESILIENT CREATURES

The researchers caution that they do not yet know the relative importance of larvae that are hatched locally and those transported down the coastal current. But if the latter are an important force, natural variations in currents, wind patterns, and ocean temperature could considerably influence the lobster fishery. A slight change could deposit commuting larvae in deep water (where they may not survive) or on sand or mud bottoms (where they make a quick meal for fish).

"It's entirely possible that oceanographic factors are playing a much larger role in lobster demography than are the lobster catches," Mr. Steneck says. "That's almost heresy to say in a world that's so seriously overfished, where so many stocks have been entirely extracted But lobsters have shown themselves to be highly resilient."

Most scientists and fishermen, though, maintain that the drastically increased harvest rates of late can't be maintained. If natural variations in the ocean have driven the lobster boom, the marine patterns could well shift back and send populations plummeting. "You can't keep taking lobsters at this level and intensity forever, at least according to everything we know," says Ms. Cowan, tagging another tiny lobster on the darkening shore of Friendship Long Island.