HARPSWELL – The tide is dead low as Diane Cowan lifts up barnacle- and seaweed-covered rocks at dawn’s first light.

Cowan is on the lookout for baby lobsters, something she and a volunteer network from Massachusetts to far eastern Maine have been doing month after month for more than a decade. Here at Lowell Cove, the number of juvenile lobsters has increased fourfold in recent years, indicating plentiful crustaceans for years to come.

At the same time, however, the water temperature in this picturesque inlet has risen fast – raising concerns about the future of Maine’s most valuable fishery. The lobsters, she fears, could begin dying off if the temperature keeps going up.

“It’s gone up 10 degrees between 1993 and now,” Cowan says as she puts small lobsters – some as tiny as a fingernail – in plastic tubs. “If it does that again, they’re gone. They’re cooked.”

Cowan, 46, is a scientist who has made lobsters her life’s calling. Every month for the past 15 years, she has counted and cataloged juveniles the hard way – by hand.

She puts up with subzero temperatures, ferocious winds, ruthless insects, and feisty lobsters that like to pinch. If low tide comes in darkness, she works with a lamp strapped to her head.

Some say she’s obsessed. You’ll get no argument from her.

“I think of these lobsters kind of as my children,” she says.

The result is the most comprehensive data around for juvenile lobsters and the nurseries where they live. There are other scientists who survey juvenile lobsters, but nobody has the information she does, said Andy Solow of the Woods Hole Oceanographic Institution in Woods Hole, Mass. Cowan’s data give an idea of where lobsters stick around when they first land on the bottom, where they grow up and where they’re eventually captured by lobstermen.

“Her dedication is unbelievable,” Solow said.

Cowan was inspired to start her lobster survey 15 years ago here at Lowell Cove, which is lined with wharves stacked high with lobster traps. She and a friend were putting in a kayak when she noticed two young boys flipping over rocks for fun in search of little lobsters.

That’s when she realized the cove was a lobster nursery, full of juveniles that would feed the future lobster supply for Maine’s 6,000 lobstermen. A few months later, she had students from Bates College, where she was teaching, surveying the area.

In time, Cowan formed a nonprofit called The Lobster Conservancy, through which she set up and trained a network of volunteers who survey juvenile lobsters April through November at other spots in New England. She shares her data with local, state and federal officials as well as lobstermen in an effort to better understand the prehistoric creatures.

“Lobbie!” she cries out on a recent morning as she locates a tiny lobster under a rock. Over a two-hour period, she locates more than two dozen juvenile lobsters, or “lobbies,” in the intertidal zone where they find shelter under rocks.

Speaking loud for a tape recorder in her pocket, she describes the surrounding habitat, with its mussels, barnacles, seaweed, worms, crabs and fish. She makes observations about the lobster’s claws, gender, antennae, color, length and hardness of shell.

She later surgically implants tiny magnetized “tags” in each lobster that can be recognized by a specialized metal detector if she captures the same lobster at a later date. She has tagged more than 15,000 lobsters over the years.

For now the lobster population appears strong in the Gulf of Maine, North America’s lobster breadbasket. The lobster abundance has gone up at 22 of Cowan’s 25 survey sites in recent years.

Those findings are important in a region where lobster contributes to the livelihoods of thousands of people and feeds summer tourists. In Maine, the 2005 lobster catch was more than 67 million pounds valued at $311 million.

But Cowan is concerned about global warming, which she thinks contributed to the lobster falloff in southern New England in the late 1990s. (Other theories list contributing factors that include overfishing, disease, pollutants and predators.)

If the ocean continues to warm up, Cowan thinks it could affect the lobster ecosystem as a whole – lobsters will move east and north in search of colder waters, grow faster and reproduce at a younger age. That, she says, could spell trouble.

“I think global warming is real and I think it’s had a detrimental effect on lobsters south of Cape Cod,” she said. “And it could do the same in Maine.”

Lobstermen put a lot of stock into what Cowan has to say, said Bob Waddle, a former fisherman who owns Quahog Lobster Co. in Harpswell.

They know of her dedication and value her data, which can be used to predict future catches.

“They call her Dr. Lobster,” Waddle said.

In fact, Cowan holds a doctorate in marine biology from Boston University. Some call her the Jane Goodall of lobsters, comparing her work to Goodall’s decades of work with chimpanzees.

Cowan has known since the ninth grade that she wanted to study lobsters. She wears clothes with lobsters on them, and a silver lobster dangles from a chain around her neck. Her vanity license plate reads “Lobbie.” She lives alone on an island with her dog, Bear, and hauls research lobster traps from a canoe.

Get her talking about lobsters and she’ll tell you about coming across blue, yellow and bright orange varieties or how she once found eight juveniles under a single rock. She says half of all lobsters in the wild are “left-clawed” and half are “right-clawed,” and that the biggest lobster on record is 45 pounds – which would be taller than she is if it were stood on end.

But even with all that, she is more impressed with how little is known about them.

“We are so ignorant about lobsters,” she says. “That’s what amazes me, is how much is not known.”

Even after 15 years of looking under rocks, Cowan’s passion and curiosity still burn bright.

That enthusiasm can be contagious, says state Rep. Leila Percy, who is co-chair of the Legislature’s Marine Resources Committee. Cowan regularly speaks to the committee and brings live lobsters to the State House to give lawmakers a better understanding of the animals.

“When a lot of scientists talk, it’s like Greek,” said Percy, D-Phippsburg. “Diane’s gift is that she can help the average citizen understand how important it is to take care of the lobster stock.”