The Secret Life of Lobsters (14 page)

B
y the time a group of London entrepreneurs settled Jamestown, Virginia, in 1607, the islands along Maine's rocky coast were already overrun with another type of Englishman. Motley bands of convicts, barflies, and kidnappees—anyone destitute enough to be forced into service aboard a long-distance fishing boat—were camping out on the islands and drying cod. In the early 1600s more than three hundred vessels from all over Europe were fishing in Maine waters, crewed by ten thousand men.

The English didn't have the salt their Continental competitors possessed for preserving cod. So instead, they dried their fish on the islands before shipping the catch to Europe. At first these island drying stations were little more than ragtag summer communities. But soon handfuls of these men, perhaps the ones who had the least reason to return home, were choosing to freeze through a winter on a Maine island that was stocked with firewood and fish sticks rather than puke all the way back to England in the hold of a stinking ship. In the spring of 1622, when the Pilgrims in Plymouth were on the brink of starvation, they headed north to beg food from a community of fishermen who were staying fat eating dried cod on Damariscove Island, a slash of land that punctuates the sea five miles off the coast of western Maine.

On a nautical chart, Damariscove Island looks like a vertical hourglass that has been stretched to its two-mile length by the pull of the North and South Poles. Its slim profile is con
stricted in the middle, as though by a corset. High tide has the effect of drawing the corset tighter, so that only fifty yards of land remain above water at the island's waist. On either side of this waist is a nearly identical cobblestone cove. One faces east, the other west.

Damariscove Island acts like a breakwater out in the ocean. Strange things have drifted onto the island in days gone by. One tale has it that in the seventeenth century, the island's English owner was beheaded and dumped into the sea by Native Americans while he was on the mainland. His body is said to have washed up on the island's shore along with his dog, which had jumped in after him. The island is supposedly still haunted by the ghosts of the captain and his loyal hound.

On a gray November day in 1987, Bob Steneck's graduate student Richard Wahle donned his scuba gear, tipped backward over the gunwale of his skiff, and splashed into Damariscove Island's eastern cove. He was looking for baby lobsters, not ghosts, but the place was so empty it felt haunted. Rick swam along the bottom, combing the rocks. The island was near his lab at the University of Maine, and he'd received a tip from a fellow scientist that baby lobsters had been spotted around the island in the past. The cove looked like the perfect place for lobster young, with its warm shallow water and dense cobble flooring—a mix of stones and small boulders. Rick saw a few older lobsters, but no babies. Wondering if they might be hiding in the crevices between rocks, he picked apart the stony bottom but found nothing. He'd brought along two assistants from the lab, and their searches came up empty too.

The divers surfaced and clambered back aboard the skiff. The day was overcast and eerily calm for November. Rick motored around the island to the western cove and again the divers pulled on their fins. Underwater it was a mirror image of the eastern cove. Rick swam to the bottom and picked up a rock. This time he found a tiny lobster underneath. The creature was only an inch long, and with a flick of its wee tail it disappeared into a crevice. Rick looked under more stones and
found more tiny lobsters. Within minutes he knew that he had uncovered the secret for which he'd been searching.

By the mid-1980s, the question of where floating lobster larvae landed on the bottom and transformed themselves into fully formed lobsters had become one of most maddening mysteries of lobster science. Four hundred miles northeast of where Rick was diving, in a cove on Isle de la Madeleine in the Gulf of St. Lawrence, a Canadian biologist had recently discovered a concentration of baby lobsters that suggested an answer, and Rick believed he was looking at something similar—a lobster nursery. What Rick didn't know yet was that he hadn't stumbled onto just any nursery. The western cove of Damariscove Island contained possibly the highest concentration of baby lobsters in the world.

Rick had first discovered that treasures lay beneath the waves when he was ten. His family was snorkeling in the British Virgin Islands when a man introduced himself as Her Majesty's Salvager. The next day Rick and his parents found themselves motoring out to sea aboard the man's boat. After they had lost sight of land the man shut off the engine and threw over an anchor. While Rick's parents watched, Her Majesty's Salvager hoisted a scuba tank onto their son's small back and told them not to worry, the tank's lack of a pressure gauge was no cause for alarm.

Treading water on the surface, Rick hyperventilated. Her Majesty's Salvager calmed him, and a minute later Rick was submerged in thirty feet of emerald sea, rays of sunlight sparkling around him like strings of gemstones. He hovered over the site of a shipwreck. Tropical fish darted past remnants of a hull and rigging. Cannon lay on the bottom, encrusted with coral.

After graduating from the University of New Hampshire in 1977 Rick took a job monitoring marine life around the site of the Seabrook nuclear power plant on the New Hampshire coast. Underwater Rick counted lobsters among the creatures he studied, but paid them little heed. He spent hours engaged in such tasks as sucking up algae and worms for later study
using an underwater vacuum cleaner. Though less romantic than exploring Caribbean shipwrecks, the underwater world off the New England coast captivated Rick just the same. To find terrain on land that was equally free of human habitation required a journey by car of several hours. With a scuba tank Rick could escape from humanity in minutes.

Rick next earned a master's degree studying shrimp in San Francisco Bay. He returned east in 1982, took a job in a natural-history museum, and got married. On a trip to the University of Maine he met Bob Steneck.

What Rick liked about Bob's approach to ecology was the way Bob saw the world not in minutes, hours, or even days, but in hundreds, thousands, and millions of years. When Bob talked about organisms interacting in the wild, whether it was sea urchins consuming seaweed or lobsters fighting for shelter, he always asked what evolutionary process lay behind the behavior. During his research in the Caribbean, Bob hadn't been content to observe the relationship between coralline algae and the snails that ate it. He'd also drilled holes into the reefs to see what the algae had looked like in the past. Then he'd sorted through museum fossils to reconstruct the algal forms and associated mollusk species that had grazed on the algae millions of years before that. Rick enrolled at the University of Maine as Bob's first Ph.D. student in 1985. Rick learned to chant Bob's mantra of ecology—patterns, processes, mechanisms—and turned his attention to the American lobster.

From Bob's censuses of lobster neighborhoods, Rick knew that the number of lobsters in any given location might be limited by the number of hiding places in the rocks. Immersing himself in the latest scientific literature, Rick learned that other researchers had recently proposed similar ideas.

In Woods Hole, Massachusetts, a pair of biologists at the National Marine Fisheries Service had analyzed the data Canadian researchers had collected off Prince Edward Island in the 1950s and 1960s. The data indicated that high numbers of larvae didn't necessarily result in high numbers of lobsters, and the new analysis had concluded that a fixed amount of
shelter space might cap the entire lobster population at a fixed upper limit, year after year. In Italy, a fisheries expert at the United Nations had proposed that the fractal geometry typical of the natural world—many small spaces, fewer large ones—could even be used to predict, mathematically, the degree to which high numbers of small lobsters would be limited by the number of appropriate hiding places as they grew bigger, resulting in lower numbers of large lobsters.

In the study of population dynamics there was a term for this sort of limiting factor—a demographic bottleneck—and Rick discussed it with Bob. No matter how many offspring a population produced, the young would have to squeeze through the bottleneck to reach adulthood, and only a certain number could fit. For whatever reason, excess young would die off. Lobster abundance could fluctuate below this limit, but couldn't rise above it.

Scientists in New England, like those in Canada, knew that lobster larvae floated off the coast during the summer and that, a few years later, young lobsters showed up in fishermen's traps. What happened in between was the mystery. If it was the limited number of shelters that was causing a demographic bottleneck, Rick suspected the bottleneck occurred sometime during this cryptic period of early life. Over millions of years, evolution had clearly favored lobsters that fought aggressively to secure protective cover. But when, exactly, in the young lobster's life did shelter matter most, and why?

 

The process of shedding its shell so dominates the life of a lobster that not until it has been living for ten or fifteen years does the interval between molts lengthen enough for the animal to enjoy a period of uninterrupted existence, when it is neither preparing to shed nor recovering from its most recent shed. But at least for a lobster proper, living a rockbound life on the bottom of the ocean, the new shell will always look like the old one. That can't be said of an infant lobster before it settles down.

As an embryo, the lobster begins life as a speck in the mass of dark green yolk inside the egg. Gradually the embryo metamorphoses into what, under a microscope, comes to resemble a translucent louse wrapped in a ball of orange cellophane, topped with an oversize pair of eyes. This period of transformation alone requires the embryo to shed its tiny shell some thirty-five times while still within the egg, developing an increasingly complex body plan with every molt. After hatching, the larva molts through yet another succession of body forms that look like miniature shrimp with spikes. Not until the creature is ready to settle on the ocean bottom does it look like a lobster.

The lobster larva floats near the surface for several weeks. Attached to its legs are paddlelike appendages that make for snazzy acrobatics—mostly somersaults—but aren't much use for covering distance. Then, between its existence as a floating larva and its life as a fully formed bottom dweller, the animal undergoes an identity crisis. It molts to what biologists have termed a “postlarva.” The postlarva is about three-quarters of an inch long and possesses the exact appearance of a miniature walking lobster. For the postlarva, however, walking is much too slow.

A fully formed, bottom-dwelling lobster can fling itself backward with rapid contractions of its abdominal muscles, but this emergency escape mechanism is so lacking in grace and control that it can hardly be considered real swimming. By contrast, the tiny postlarva swims nearly as well as a fish, propelling itself forward through the water on a reliable trajectory and at a constant speed by beating the swimmerets under its tail. This is the only time in the lobster's life when the animal can swim forward, and even though the minuscule postlarva is smaller than a baby lobster, scientists have affectionately bestowed it with a grand nickname—the “superlobster.” Like a miniature Superman, the animal flies through the water with its little claws outstretched. Its adventures are all the more heroic for being brief. Life as a superlobster seldom lasts more than two weeks. Soon it must settle to the bottom and undergo
its final shape shift by shedding its shell yet again. What emerges is an inch-long baby lobster that has lost the ability to swim.

The swimming skills of superlobsters were noted in the scientific literature as early as the turn of the century. But it was Stanley Cobb, the pioneering investigator of lobster behavior at the University of Rhode Island, who demonstrated that superlobsters swim for a reason.

As a graduate student in the 1960s, Stan started with an experiment involving twenty-four plastic dishpans and 120 superlobsters. Six of the dishpans he left bare. The remaining pans he outfitted with bottoms of either mud, sand, or coarse gravel. In the latter case, the gravel provided crevices that a superlobster could tuck itself into. Stan positioned each dishpan under a separate supply of running seawater and dropped five superlobsters into each pan. He fed them a daily dose of brine shrimp and watched to see which superlobsters would settle to the bottom first.

Each superlobster swam around exploring its dishpan for more than a week before any committed to becoming lobsters. But when the settling and molting began, the superlobsters that could hide themselves in nooks between chunks of gravel were, on average, two days ahead of those in the sand pans, who busied themselves trying to dig a depression first. The superlobsters in mud, and in dishpans with bare bottoms, lacked any way to hide and were the last to become lobsters. Clearly, locating shelter was a priority for superlobsters. Without a hiding place they would delay settling to the bottom. Stan thought they must be holding out in the hope of finding more protective terrain.

Watching superlobsters in dishpans was one thing. Trying to track them through the ocean was quite another. That didn't stop Stan. Once he'd finished his Ph.D. and secured a teaching post, he talked a handful of colleagues into spending the month of July snorkeling in Buzzards Bay searching for swimming postlarvae—creatures about the size of kidney beans. In shallow water the divers actually spotted a few superlobsters. To
augment their observations they also released seventy lab-reared superlobsters of varying ages. Some were just a day or two old; others had been superlobsters for more than a week.

The scientists discovered that superlobsters swam in two different modes—“claws together” and “claws apart.” The latter was slower but useful for hunting at the surface. Claws-apart superlobsters frequently paused to attack foam bubbles floating on top of the water. The behavior made sense once the scientists witnessed a couple of superlobsters carrying winged insects they'd dragged under with their claws. Other superlobsters were seen making a meal of floating crab larvae. When a superlobster near the surface encountered a less appetizing object—a weed or twig, for instance—it stopped methodically, backed up, circumnavigated the obstruction, and resumed travel along its original course.