Read The Secret Life of Lobsters Online
Authors: Trevor Corson
The Secret Life of Lobsters (15 page)
In claws-together mode, the superlobsters became torpedoes. Streamlining their bodies, they dove into deeper water, sometimes cruising horizontally a foot beneath the surface, other times making a beeline for the bottom. The younger superlobsters, having been in the postlarval stage only a few days, were eager explorers. After swimming like fish for several yards they would dart to the bottom and scurry around on foot, investigating places to hide. As often as notâespecially if the bottom was featurelessâthey would clap their outstretched claws together and, like Superman leaping over a tall building, launch themselves back up so they could fly to a new location.
The older superlobsters, however, were less inclined to leave the bottom once they'd landed, especially if they'd found places to hide. They seemed to hear the ticking of their biological clock. After a larval existence of somersaulting and a postlarval existence of flying, the freedom of weightlessness was now giving way to the harsh realities of growing into a proper babyâgravity, and the need for protection.
Back in the lab, one of Stan's graduate students built a seawater racetrack and recorded superlobsters swimming at speeds of nearly twenty centimeters per second. The super
lobsters did their fastest swimming during daylight, in contrast to the nocturnal habits of grown lobsters. Stan and his student guessed that superlobsters might use the sun for navigationâmany arthropods tap into celestial cues to establish direction, and some shrimps have been shown to orient themselves in relation to planes of polarized sunlight in the water. The scientists calculated that in five days, a superlobster could swim nearly twenty-five miles. But where, exactly, were they going?
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In the western cove of Damariscove Island on that gray November day, Rick Wahle had lifted more stones off the bottom and discovered more tiny lobsters, but he'd also discovered a problem. When he disturbed the stones a cloud of sediment obscured his view. It was obvious that the cove was a nursery for lobster babies, but with clouds of silt everywhere, it was difficult for Rick to get an accurate estimate of their numbers.
Recalling his days vacuuming up algae and worms near the Seabrook nuclear power station nearly a decade earlier, Rick returned to Bob Steneck's lab and rummaged through a pile of unused sections of PVC pipe, but none were quite right. A trip to the hardware store secured what Rick wantedâa section of wide plastic pipe three feet long, along with several sheets of flexible window screening. Rick drilled a hole near one end of the pipe and attached a flexible hose, running the other end of the hose to an old scuba regulator on a tank of compressed air. He folded the window screening into a bag and strapped it over the other end of the pipe, then stood back to admire his handiwork. It looked like a makeshift bazooka.
The following summer Rick and an intern piloted their skiff back out to Damariscove Island's western cove, this time carrying Rick's underwater vacuuming device. They slipped the contraption into the water and swam with it down to the cobblestone floor fifteen feet below the surface. Similar devicesâcalled suction samplers or airlift samplersâwere commonly used to collect things like clams as well as algae and worms,
and using one to collect baby lobsters seemed like a reasonable idea. But Rick wasn't sure it would work.
Holding the pipe upright, Rick twisted open the valve on the tank. A stream of bubbles shot through the hole and rose the length of the pipe before bursting out through the mesh bag at the top. Rick gave his intern a thumbs-up, then lowered the pipe while the intern lifted stones out of the way. The stream of air generated a suction that inhaled everything into the pipe in a blur. When Rick closed the regulator valve and detached the mesh bag, the sand and silt had mostly blown through the mesh and away from the divers. What remained inside was a collection of shell hash, pebbles, and baby lobsters.
After making some modifications to his suction sampler, Rick was ready to put it to use. He first searched for other nurseries over a ten-mile swath of coastal sea. Between Damariscove Island, which lay exposed five miles offshore, and Pemaquid Harbor, an estuary five miles inside a narrow bay, Rick chose five locations. Each contained three kinds of underwater terrain in close proximityâopen bedrock, sediment, and cobble.
Rick had read Stan Cobb's papers on superlobstersâthe little postlarvae that swam to the bottom and transformed themselves into the babies Rick was studying. If Maine's superlobsters were like the ones Stan had studied in dishpans, they would avoid both the open bedrock and the less protective sediment. Instead, they would seek out hiding places among the nooks and crannies in the cobbleâand there they would stay, molting to become babies. With assistance from Bob and a team of student divers, Rick set out in the summer of 1988 to fulfill his role as an ecologist by mapping the patterns of distribution and abundance of the natural world.
At each site, Rick and his divers began by throwing down a square frame made of rebar, a half meter on a side and spray-painted orange, called a quadrat. By delineating random pieces of bottom that were always exactly the same size, the quadrat helped the divers generate statistically useful data from which they could extrapolate.
When working on cobble, the divers removed the stones inside the quadrat while suctioning away the silt underneath. On mud bottom, the divers suctioned six inches of surface layer away because baby lobsters had been known to drill U-shaped tubes when the mud was deep enough. Sand was too loose for burrowing, so there the divers didn't bother with suctioning but compiled their censuses by sight, as they did for solid bedrock. In a matter of weeks, Rick and his team had sampled more than 350 quadrats and blown through some 120 tanks of air.
The pattern was astonishingly clear. Superlobsters settled, and baby lobsters lived, almost exclusively in shallow coastal seafloor where more than two-thirds of the bottom was composed of cobblestones at least several inches in diameter. Bedrock and sediment were mostly bare of babies.
But the seafloor along the Maine coast was mostly bedrock and sediment. Rick calculated that only about 10 percent of the bottom in his study area contained the kind of prime cobble that baby lobsters required. If the rest of the Maine coast was similar, then the terrain of the seafloor itself might well be the bottleneck that limited the lobster population.
That made the bottleneck almost impossibly tight. Yet there was evidence that something made it even tighter. Even when prime cobble was present it could lie barren. Why, for instance, on the eerie island of Damariscove, was the cobble cove facing west home to more babies than anywhere else, while the cobble cove facing east was home to little but ghosts?
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Catching insects with a butterfly net hanging off a helicopter might have been easier. Lewis Incze, an oceanographer at the Bigelow Laboratory for Ocean Sciences, was an expert at catching the larvae of crustaceans, and he'd offered to use his remarkable skills to help Rick Wahle unravel the mystery of Damariscove Island. While Rick counted babies on the bottom, Lew searched for superlobsters on the surface.
Lew stole a glance at the sea ahead, then returned his gaze to the net skimming along the water from a boom off the side of the boat. The tiny holes in the net's one-millimeter mesh barely let through water, let alone superlobsters, and Lew had to make sure a floating log or tangle of seaweed didn't tear the net. A rectangular frame at the mouth of the net was attached to a pair of miniature water skis, which kept the lower edge of the opening at a depth of half a meter. If there were superlobsters swimming at the surface, Lew's net ought to snag them.
The boat was running west in a line straight from Damariscove Island. At the end of the tow Lew hauled in the net and dumped out the contents into a sorting tray. A research assistant helped Lew comb through the pile of debris, seaweed, and plankton while the boat's captain steered toward the beginning of the next tow. With the height of the superlobster season upon themâit was the middle of Augustâthe researchers were repeating this routine sixty to seventy times a day.
Lew liked being on the water. He was an avid sailor, and his office at the Bigelow Laboratory in Boothbay Harbor was just a twenty-minute cruise from Damariscove Island. Lew had grown up in Maine and from the age of five had spent his summers living on a tiny island with a single cabin. His graduate work had taken him to the opposite edge of the continent, where he'd earned a Ph.D. chasing the larvae of Alaskan snow crabs through the Arctic climes of the Bering Sea. He was glad to be back in his old neighborhood, because the Gulf of Maine was a unique natural laboratory for the study of oceanography. Whether Lew was at work on a research cruise or enjoying a summer sail, the gulf's constant movement intrigued himâits cold deep currents, its warm shallow eddies, its turbulent upwellings, its prevailing winds. The question of how the physics of the sea interacted with the biology of its creatures fascinated him.
After the last tow on the western side of Damariscove Island the captain gunned the boat for the mile-long trip around the island to the eastern side. The afternoon sun had kicked up a breeze out of the southwest, a trademark of the
Maine coast in summer, and the boat wobbled on the fluttering sea. Lew had yet to analyze the numbers, but so far he'd seen an obvious pattern. On his offshore tows, Lew had been catching similar numbers of superlobsters whether he was on the east or west side of the island. That wasn't the case near shore. When he trolled over the western cobblestone cove where Rick's nursery lay, Lew caught superlobsters in numbers that often exceeded his catches offshore. But above the cobblestone cove on the eastern side, Lew's net usually came up empty.
To a sailor like Lew, who'd spent his boyhood on the coast, the puzzle wasn't difficult to solve. Lew compared his data with wind readings from a weather buoy anchored near Damariscove and saw that the direction of the summer breeze easily accounted for the patterns he and Rick observed. Damariscove Island's narrow, north-south profile ran nearly perpendicular to Maine's east-west coastline. The southwesterly wind was pushing the surface water containing superlobsters up against Damariscove's western edge. At the same time, it blew across the island's narrow waist and pushed surface water away from the eastern edge.
Combined with the effects of tidal currents around the island, the southwesterly breeze was creating a superlobster hot spot on one side and a corresponding shadow on the other, despite the presence of hospitable cobble in both places. Most likely, similar effects had been in play when the beheaded ship captain and his ill-fated dog had washed ashore three centuries before.
Given how common the southwesterly breeze was along the Maine coast, it seemed likely that cobble facing east would almost always catch fewer superlobsters than cobble facing west. The effect would be an even narrower demographic bottleneck than could be accounted for by the terrain of the bottom alone. Back at the Darling Marine Center, Rick Wahle chanted Bob Steneck's mantra of ecology to himselfâpatterns, processes, mechanismsâand contemplated the picture that was emerging.
The pattern was obvious. Baby lobsters were concentrated
in cobble, particularly in coves facing the prevailing southwest breezes of summer. The general processes responsible for that pattern were becoming clear. Water movements delivered postlarvae against western shores, and then the little superlobsters swam to the bottom and, if they found cobble, molted to become bottom-dwelling babies. The mechanisms behind the processes were more specificâthe physics of wind-forcing on surface water, for example, and the navigational and shelter-seeking behaviors that were hardwired into the superlobster's nervous system.
But to understand the behavior of superlobsters Rick had to think not in minutes, hours, or days, but, as Bob had taught him, in hundreds, thousands, or even millions of years. The process of evolution had selected some superlobsters over others, favoring the behavioral traits in evidence today. Superlobsters carrying a genetic code that instructed them to find hiding places immediately had survived and passed on their genes. The rest had died. Why?
The ecological training Bob had given Rick had included the unpleasant lesson that evolution was as often a matter of death as of survival. It wasn't long before Rick discovered the gruesome fate awaiting baby lobsters that never found the nursery grounds.
W
arren Fernald gaffed his next white-and-yellow buoy and tapped the throttle of the
Mother Ann
down to idle. He spun the wheel to port so the boat would drift in a circle back toward the trap and take the strain off the rope, then tugged up a few feet of line and flipped the slack over the hauler pulley. He pushed the lever on the bulkhead that powered up the hydraulic hauler and threaded the rope between the spinning steel plates. The hauler whined, tightened the line, and reeled it in.
Warren allowed his eyes to wander over Little Cranberry Island in the distance. Before shifting his gaze back to the rope, Warren glanced over his shoulder to check on his son Dan, who was hauling traps nearby in the
Wind Song
. As a precaution, the Little Cranberry fishermen kept an eye on one another.
Warren had learned the hard way how easily a lobsterman could find himself near death. One winter afternoon he was fishing without a sternman. He threw his last trap of the day overboard when a nail protruding from the trap caught his glove and dragged him to the transom. His boots left the deck and he was about to tumble over the stern when the glove came off. Head and shoulders over the water, he had lain there and watched the white shape of a hand sink out of sight.
Another day Warren had thrown a pair of traps off the rail and gunned his engine, only to see that he'd stepped inside a
loop of buoy line. The rope pulled tight around his ankle and dragged him aft, away from his engine controls. He dived to the deck, lodged himself under the stern, and wrapped his arms around the mast of his riding sail while the boat raced out of control. As the boat dragged the two traps through the waves, the rope cut into Warren's ankle. In moments the force would pull him overboard. He let go of the mast with one hand and fumbled in his pocket for his jackknife. Opening the knife with his teeth he sawed frantically at the rope until tendrils of twine splayed with the strain and then, with a pop, finally the rope parted. He'd lost his traps but not his life.
Warren stole another glance at Dan. Every parent worried about the safety of his or her children, and perhaps no one more than a commercial fisherman who counted three fishermen among his sons. Warren had to hope that his boys would never come as close to a grisly death on the water as he had. Given the history of Little Cranberry, though, such hopes might be hard to fulfill. The sons of the island had been dying at sea for nearly two centuries.
Before lobsters were worth trapping, fishermen from Little Cranberry Island perished in pursuit of another catchâthe cod. Little Cranberry was probably settled around 1762, but the craze to catch cod didn't arrive on the island until 1803, when a man named Samuel Hadlock anchored his ninety-ton schooner,
Ocean,
in the harbor. Hadlock had encountered a streak of bad luck on Mount Desert Island. His house had burned to the ground, he'd sunk two boats, and his father had just been hanged for murder. Moving to Little Cranberry offered a fresh start.
To restore his fortunes Sam hired a crew of local men and sailed for the Grand Banks, a thousand miles away. Sam's luck improved and he filled his hold with fish. He dried them on the shore of Labrador and sailed east, running French and British blockades to sell his catch in Portugal at premium prices. After a trading run to the Caribbean, Sam returned to Little Cranberry a rich man. He bought a fleet of schooners and transformed the little island into a hub of the New England cod
trade. At any one time, six hundred ships might be seen in the waters around the Cranberries and Mount Desert.
But the price of prosperity was steep, for catching cod offshore was dangerous work. Almost every family on Little Cranberry Island sacrificed sons to the deep. Sam in particular paid in proportion to his wealth. By the time he died at the age of eighty-four, three more of his ships had sunk and four of his five sons had died at sea. Cod stocks in the western North Atlantic dwindled, and on Little Cranberry Island, the Hadlock dynasty had waned, making way for a new dynasty built on lobsters. By the late twentieth century, the Fernald family had risen to ascendance.
Aboard the
Mother Ann
, Warren finished cleaning out his trap and shoved it overboard. As the buoy line played out over the stern, he steered his boat toward the white hull of the
Wind Song
to greet his son. When Warren pulled alongside, Dan had just gaffed another buoy and was slipping the rope through the heavy steel housing of his hauler pulley. He wound the rope into the sheaves of the hauler and started it spinning before turning his attention to his father. Warren had gotten a couple of words out of his mouth when Dan's rope went taut. There was a crack like a rifle shot and the pulley housing leaped from its mount and slammed into Dan's jaw, knocking him across the boat and onto the deck, where he lay inert, limbs splayed at awkward angles.
“Dan!” Warren shouted.
A full minute passed without a sign of life. Warren maneuvered the
Mother Ann
toward the side of the
Wind Song
so he could lash the boats together. He saw Dan regain consciousness, his head battered but intact. Another close call.
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Hunched over his lab bench at the Darling Marine Center, Rick Wahle held another baby lobster on the tip of his thumb. Squinting, he used a pair of calipers to measure the length of the animal's carapaceâsix millimeters. Rick put down the calipers and lifted a piece of fine nylon thread. He'd tied a loop
the size of a pinhead in one end of the line. He dipped the loop into a dish of superglue. A tiny drop of the glue stuck to the thread. After blow-drying the moisture off the lobster's back, Rick touched the drop of glue on the thread to the top of the lobster's carapace. It adhered instantly.
Rick sat back in his chair, took a deep breath, and expelled the air from his lungs. Rolling his head to stretch the muscles in his neck, he wondered how he had ever come up with the idea of putting a baby lobster on a leash, let alone doing it to over two hundred specimens.
Stanley Cobb's experiments had shown that when a superlobster's biological clock ran out of time, it would swim down and molt into a bottom-dwelling baby even when all it could find was open bedrock or bare sediment. If this happened in the wild and the lobsters survived anyway, then Rick's hypothesis that baby lobsters required cobble would be wrong. But if they failed to survive, then Rick would have found additional evidence of the demographic bottleneck. Only baby lobsters hiding in a cobble nursery would live. Those that failed to find cobble would die.
The fine nylon thread and superglue worked only on the smallest lobsters. On his one-and two-year-old babies Rick tied a piece of braided fishing line snug around the animal's carapace like a belt and attached a steel fishing leader. The lobsters would reach down and grab the leader with their claws, but they couldn't break the metal. Rick dangled each animal in the air on its leash and bounced it up and down a few times to ensure that the tether was secure before dropping the baby lobster in its own private dish.
Borrowing Bob Steneck's leaky houseboat, Rick took a summer intern from the lab and moored the boat in the bay. Rick and his assistant splashed overboard, spread patio tiles out at intervals of a few feet, then returned to the boat. Rick had sorted his pretethered baby lobsters into three size categories. With the lobsters in bags, they dove again and clipped each lobster's leash to a tile. Once in place, the lobsters scurried frantically about their individual patios, but like a puppy
tied to a stake, each lobster hit the end of its tether before it could run away.
The next day Rick and his assistant dove again. All five of the largest baby lobsters sat calmly on their patio tiles in the sunshine. But a few feet away, while two of the mid-sized babies remained, next to them were three empty loops of fishing line. And on the tiles that had held the smallest babies, all that remained were five wispy strands of nylon, each ending in a tiny chunk of lobster shell still stuck to a ball of superglue.
Rick positioned an underwater video camera next to the patio tiles and ran the video feed to the surface. Over the course of a week, he and his assistant tethered fifty more lobsters to the patio tiles in batches. The scientists fixed mugs of hot chocolate, then sat in front of the TV on the houseboat to watch what happened. A type of small fish called a sculpin would often appear, circle a hapless baby, then clamp its toad-like mouth over the little lobster and shake it until the lobster had disintegrated enough for the fish to tug it free. Another type of small fish called a cunner, with a smaller mouth, tended to strike once, swim away, and return to strike again, the lobster dangling from its tether in successive states of dismemberment.
Each little lobster's death was a heroic sacrifice for the sake of science. The experiment revealed the natural processâfish predationâthat enforced the demographic bottleneck. A superlobster that failed to find shelter before transforming itself into a baby would become fast food for these enforcers. Rick's smallest babies were usually attacked by fish within fifteen minutes. The mid-sized babies sometimes lasted an hour. The biggest babies usually remained unscathed. The lobsters in this last category were about the same size as the smallest lobsters that Rick had found wandering across open terrain during his surveys. Having passed successfully through the bottleneck, they had grown large enough not to be attacked. So far, Rick's theory that small lobsters needed shelter was holding water.
The leaky houseboat wasn't. The University of Maine had started to fear for the safety of the students in Bob Steneck's lab, and shortly thereafter the craft was condemned.
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Jack Merrill had never gotten around to circumnavigating the globe in his sailboat. But in search of lobsters he'd made a habit of running the
Bottom Dollar
twenty miles offshore to a tiny, distant island that had been namedâafter its big brother, Mount Desert IslandâMount Desert Rock. The remote islet was little more than a half acre of granite protruding from the sea, topped by a stone lighthouseâprobably the most exposed lighthouse in the United Statesâand a keeper's lodge.
Lobstermen had put a stop to the government's additional increases in the minimum legal size of lobster, and Jack hadn't noticed any dispersal of legal-sized lobsters away from the coastâthe consequence Bob Steneck had warned against. But in a sense, Jack was a bit like a large lobster himself. As the number of traps escalated in the shallows, Jack preferred to give the other lobstermen space and seek out new territory in deeper water. His powerful boat gave him that option.
It was an option fraught with danger. The winter storms that ravaged the Rock were so wild that waves had once rolled a seventy-five-ton boulder from one side to the other. The lighthouse keeper and his family had routinely locked themselves inside the tower with a winter's worth of provisions lest they be swept into the sea. To go outside they had tethered themselves to the granite with the stoutest rope at hand. Now the lighthouse was automated and the Rock uninhabited.
Jack squinted at the lighthouse in the gray December morning and guessed it was about half a mile off his stern. He checked the chart he'd spread on the bulkhead and ran his index finger along the contour lines of the underwater terrain. Just southeast of his position the map indicated a special feature on the bottom: “Unexploded ordnance.”
Fishing around the Rock was tricky enough without the added risk of hauling up a forgotten bomb or torpedo. Jack
gave the boat a drink of diesel and the engine roared. Watching his Fathometer, he circled several alternative locations and found a piece of bottom that looked promising. Despite the risks, setting traps this far from land allowed Jack the luxury of forgetting about the politics of the lobster industry. Out here he could focus on fishing.
“
Bottom Dollar
, you on there, Jack?”
Jack would have recognized that raspy voice crackling over the VHF in his sleep. It belonged to the only other Little Cranberry lobsterman crazy enough to fish this far out. Mark Fernald.
“Yo!” Jack yelled into his radio mike, not bothering to remove it from its overhead clip.
“Kinda slatty out here this morning, isn't it?”
On his chart, Jack finished plotting the path of his next string of traps before glancing again at the waves rolling toward the boat. There were days out here when the waves were so huge they could tip the
Bottom Dollar
nearly on its sideâJack had once lost twenty or thirty lobsters over the gunwale. There were days when he would decide that he wanted to watch his daughter and son grow up. On those days, instead of hauling the rest of his gear, he'd set a course for home.
“Could turn a little nasty,” Jack responded, this time tugging the mike off its clip. He scanned the horizon for Mark's boat. “Where you at?”
“Just finished setting some gear out on the ridge.”
Inner Schoodic Ridge, an underwater mountain range surrounded by canyons, was ten miles northeast of Jack's position.
“Yup. Well, don't stay out too long,” Jack laughed. Mark could drive the dockworkers back at the co-op crazy. Some days he wouldn't pull up to the wharf until the other fishermen were already home eating dinner.
Jack was happy to let Mark fish the ridge. Always interested in biology, Jack liked Mount Desert Rock for the seabirds and other marine life it attracted. As he replaced the
microphone, shearwaters were skimming the chop around his boat like stunt planes. A pair of razorbills streaked by. Sometimes gannets circled overhead and plummeted into schools of fish. Porpoises and white-sided dolphins plied the waves, and in summer bluefin tuna leaped from the water in feeding frenzies. And every so often, when Jack hauled up a trap around Mount Desert Rock, the wire cage would break the surface like a time capsule. Inside would be the shimmering bronze body of a cod.
