Biologist Michael Moore had waited all day — really, all his life — for the whale to surface, the suffering giant he thought he could save, that science had to save. It had come down to this.

Thirty meters,” Dr. Michael Moore called out.

Moore braced himself against the steel of the Zodiac’s platform tower as the boat closed in on the whale in the heaving Florida waters. Through the rangefinder, he could see the tangled mass of ropes cinched tightly around her. It was impossible to tell where the ropes began and where they ended.

This much he knew. The ropes were carving into her. Bayla was in pain.

He was tempted to look away. It was almost too much to see.

Her V-shaped spray erupted then disappeared into a mist as she slipped beneath the surface. A spot-plane circling overhead radioed. They could still see her silhouette. She hadn’t gone deep.

“Get in close if you can,” Moore said to the boat’s driver.

Bayla would come up for air again soon.

Then he would have his chance.

For nearly three decades Moore had dedicated himself to North Atlantic right whales like Bayla. He knew every inch of their anatomy, every detail of the strange and glorious physiology that made them so astoundingly powerful and so utterly defenseless against the ropes.

They were majestic and doomed, his love and his burden. He had believed he could save them. But in those thirty years he’d watched too many succumb. Saving just two female whales a year could stabilize a population that humans had driven down to just 450 from the teeming thousands that once greeted settlers to the New World.

And so he had raced down the interstate through a driving New England snowstorm after the e-mail had come.

The details were grim. Bayla had been spotted off the coast of Florida three weeks earlier on Christmas Day, 2010. Rope anchored in her mouth. It coiled around her flippers in a skein of tangled loops. With every move, it pulled tighter.

The rope was likely polypropylene, a synthetic weave favored by Northeast fishermen and lobstermen for its brute strength against the abrading forces of a rocky-bottomed seabed. Blubber was no match for it. Bayla’s body was cut open in places, as though by cheese wire.

Her back sloped alarmingly, a sign of emaciation from hauling rope more than 10 times her length, possibly for months. It was like she had been swimming with an open parachute.

Biologists from Florida and Georgia had tried to cut the ropes. But Bayla threw them off with heaves of her massive tail and stunningly quick hair-pin turns. They tried again a day later. Still they couldn’t get near enough. She was a bucking bronco.

And so they summoned Moore.

Moore had engineered something that could be a breakthrough for rescuers, a way to sedate whales at sea. The man standing to his left on the Zodiac platform held the instrument Moore had conceived for the task: a pressurized rifle tipped with a dart and syringe filled with 60 cc’s of a sedative so powerful that a few drops on human skin could kill.

Bayla was probably seven tons, but you can’t weigh a free-swimming whale. If the estimate were wrong, an overdose could plunge Bayla into a catastrophic slumber and she would drown.

Moore scanned the horizon. Fishing charters and Disney Cruise Liners jockeyed for space at the shore. Ahead, the vast reach of the Atlantic met at every point with the prickling Florida sun.

He knew that the work of a lifetime shouldn’t come down to a single moment. He was the father of four grown boys. He loved his wife. His home was an island in Marion Harbor. He had published scores of peer-reviewed papers and commanded millions in grant money.

Yet the vow he had made to himself as a young man, the thing he had dedicated his career and heart to, remained unfulfilled. For Moore, nearing retirement and running out of ideas, there might be no more chances.

Blow spouted off the port bow.

“Twenty-one meters,” he called to the man with the dart rifle.

Bayla’s hobbled body arced through the swells.

“Shoot.”

For more than a thousand years, humans hunted the North Atlantic right whale. Big, slow, and without guile, the whales often ventured up to boats, rolled over, and eyed their pursuers with peering curiosity, making for easy marks. Endowed with abundant blubber, right whales also floated after being killed. It was a grimly convenient attribute that, legend has it, afforded them their name. They were the right whale to kill.

Basques hunted them in the Dark Ages. The rest of the European continent followed. Pilgrims on the Mayflower spied right whales as they came into Cape Cod Bay, a feeding ground for the vast animals. “Every day we saw whales playing hard by us,” one passenger wrote. The ship’s master and mate lamented they didn’t have the tools to kill the whales. They soon would. An industry quickly took root in maritime New England. On a single day in January of 1700, colonists killed 29 right whales off the Cape.

Oil from right whale blubber helped propel the Colonial economy, lighting homes and stores and creating wealth and prosperity. By the time whale oil demand faded and right whales were protected from hunting in 1935, their numbers had been reduced from the thousands to some 100 in the North Atlantic.

Today, right whales remain among the rarest animals on earth. Their pursuers are whale-watching boats and a legion of scientists who track them in the hope of figuring out why their numbers hover stubbornly in the low hundreds, a population so fragile that it could be wiped out with one algal bloom.

Researchers say the peril can be traced once again to humans — this time because right whales get in our way, or we in theirs. Dubbed the “urban whale,” North Atlantic rights live along the Eastern seaboard, one of the most developed coastal zones in the world. Migrating from southern calving grounds to northern feeding climes is an industrial obstacle course for the whales, studded with pollution, noise, ships, and most devastatingly, fishing gear — often buoy-tethered ropes leading to lobster pots and crab traps.

Among whales, rights are particularly prone to getting caught in the gear, with 83 percent of those tracked by scientists bearing scars from entanglement. Their special susceptibility, researchers say, owes to feeding with open mouths — filtering tiny prey through their long plates of baleen but also taking in the ropes so common in their domain. Once snagged, the whales frantically spin their bodies trying to get free, but their gyrations instead loop the ropes around flippers and flukes. Unlike weaker whale species that tend to drown when entangled, right whales, which run to 50 feet and 60 tons or more, often have the strength to swim with the lacerating ropes for months, sometimes years.

It’s not known how many right whales die from entanglement. Scientists have recorded an average of four such confirmed and presumed deaths per year since 2008, but they believe many more perish this way unrecorded. In a species plagued by abnormally low reproductive rates, in some years with a single calf born in the known population, scientists worry that deaths from ropes could be right whales’ ultimate undoing — Moore chief among them.

In the summer of 1979, a grungy 28-foot sailboat with a scruffy crew docked in Newfoundland’s treeless peninsula of Bay de Verde, an outcropping of houses, a fish processing plant, and a bar called the Holding Ground.

Word went around that the boat’s inhabitants were long-hairs, American college students fired up by the “Save the Whales” movement who had hitchhiked to Newfoundland to study humpback whales. The students played sea shanties on concertina and guitar. They drank Dominion Ale at the Holding Ground and tried to convince fishermen that whales ensnared in cod nets were not nuisances but wonders.

Soon, a 23-year-old British veterinary student joined them.

Michael Moore was on expedition, as students’ research journeys to remote spots were called at the University of Cambridge. He wasn’t certain he wanted to spend his life tending to dogs and cats, as he had assumed he would. Studying whales was a year-long diversion as he wrestled with his career plans.

To the Americans, Moore projected quirky English certitude. He had graduated from Winchester College, an elite boarding school, and was now at Cambridge. He took his tea every day at 4 p.m. He read Thomas Hardy aloud. On his first night aboard the sailboat, as the Americans climbed into their berths in salted dungarees and cable-knit sweaters, Moore opened a leather satchel. He pulled out a pair of striped pajamas so crisp they might still have had Harrods tags attached.

In the mornings, Moore and his boat mates woke to the frenzy of gulls feasting on cod stomachs gutted by fishermen after pre-dawn hauls. They pulled on oilskins and ventured into the cold emerald bay with the boat’s hand cranked-engine belching diesel fumes. They chugged around the peninsula for hours watching humpbacks lunge at schools of capelin.

Moore dutifully jotted observations about the whales in his journal and said little to the Americans. They ribbed him for his punctually taken Earl Grey. One afternoon, he returned the volley with dry, cordial wit. The Americans were taken aback. Moore had found his way. “Beginning to relax and feel part of the machine,” he wrote in his journal. “There are some real super people around here — all fine and kind and loving.”

From the time of his childhood, Moore had felt somewhat apart. He’d been 12 when his mother told him that his father was manic depressive. The news stunned him. He’d always thought of his father as a steady rock, a country doctor content with his practice. He’d had no idea that his father was undergoing a grueling course of convulsive shock therapy or that his mother had come upon him after an attempted suicide. The family dynamic now became clear to him: his mother tended his father and his father tended his patients. Alone many afternoons, he wandered from his home, down to the railroad tracks where he kept tabs on a badger family, an experience that steered him to study the animal condition.

Now, at last, he was on the inside.

His descriptions of the whales grew animated and lively. They were grand, clever, and powerful, the sea’s benign emperors, yet astonishingly vulnerable. One day the researchers came upon a humpback caught in a cod trap under the cliffs. The whale was thrashing in panic. Other humpbacks were circling helplessly. “I need to go in and cut the net,” Moore said as he and the others watched in horror. It would have been reckless; the nets could readily have entangled him too. He was about to dive, when other humpbacks helped the whale break free, leaving Moore’s declaration flapping like the flag of an impetuous explorer who had stumbled on something but wasn’t yet sure what it was.

Moore stayed on with the researchers at summer’s end and sailed with them to the humpbacks’ wintering grounds in the Caribbean. As Christmas approached and carols played on Radio Antigua, he thought of his mother. She had died two years earlier. He thought about how burdened she had been by his father’s illness and about the guilt he’d felt for being unable to lighten her load.

One night, Moore woke in his berth. He had been dreaming of whales swimming around the coral reef where the boat had anchored. The whales were singing in the dream. As consciousness pushed aside the dream, Moore realized the calls and whistles of the whales were not the stuff of his mind but real and coming through the hull, a chorus of longing and kinship.

Surrounded by the sounds, Moore realized he would spend his life studying, helping, and learning from these creatures.

Bayla was Picasso’s new beginning.

Bayla’s mother had lost a calf in fall of 2007. It was her first, and it lived only a few months. Researchers don’t know where or why the calf died, but they assumed something catastrophic had happened when Picasso appeared without it. No right whale mother would have abandoned her young before a year spent together.

For Picasso, the death of the baby had to have been wrenching. Right whale mothers are known to swim frantically for days after the death of a calf, searching for the little one no longer at their side.

Researchers spotted Bayla for the first time on Jan. 2, 2009, swimming alongside her mother and a pod of bottlenose dolphins off the coast of Georgia.

Like all right whale encounters, the sighting of Picasso with her days-old calf was a matter of luck. In an era when wild animals are routinely monitored, their every movement documented for years running, whales are the exception. Whales can’t be banded like birds, or collared like a wolf, and implanted tags can fail after a short time. The legions of scientists who study them often can only guess their location in the depths.

Researchers catalog sightings in a database painstakingly maintained by the New England Aquarium since 1980. The database distinguishes the whales often by cream-colored skin patches that grow in the same spots where human hair sprouts — on heads, above eyes, chins, and jawlines.

Picasso had been named for the modernistic cross-hatch of splotches on her head, the result not of the naturally occurring callosities but of injuries from rope entanglement when she was 3 years old. The researchers weren’t ready to name her daughter yet. She was still so young. The name Bayla would come years later.

But they noted a distinction: Unlike the white chins of some right whales, Bayla’s was onyx black.

In her first seconds alive, Picasso would have nosed Bayla to the surface for breath — a first tenderness in a year in which she would nurse and cradle and teach Bayla the ways of the sea.

Through the winter, researchers saw Bayla and her mother swimming along the coasts of Florida and Georgia, Bayla tucked beside Picasso, safe from great white sharks. The pair began a 1,500-mile trek north as the weather warmed, their boxy bodies and oversize heads moving with unhurried calm, topping out at a pokey 6 miles an hour.

Picasso and Bayla would have crossed shipping lanes off the great ports of the East Coast and swam through the agricultural and industrial runoff of poultry and pork farms in North Carolina and factories in New Jersey and New York. The hazards, documented in accounts including “The Urban Whale,” a book edited by New England Aquarium researchers Scott Kraus and Rosalind Rolland, increased as they moved north. With every mile, the risk of collisions with crab and lobster fishing gear would have grown.

Bayla and her mother likely would have stopped in Cape Cod Bay, where their favored food was plentiful in spring, and would have arrived at their destination in Canadian waters in early summer.

The Bay of Fundy, between Nova Scotia and New Brunswick, has among the most dramatic tidal surges in the world. Twice daily, 100 billion tons of seawater rush in and out of the deep rift valley, a result, in native Micmac lore, of a giant whale’s tail splash.

Picasso was a regular in the Bay, like many right whales, returning in summer to feast on the Bay’s vast quantities of shrimp-like copepods, zooplankton rich in nutrients that scientists suspect are gathered there by the force of the tides.

Bayla’s mother would have dived to feast on copepods while Bayla, initially, stayed at the surface.

With a calf’s curiosity, Bayla would have taken stock of her new world with right whales’ black and white vision, registering the life around her in varying shades of gray — the swimming mola-molas and basking sharks, the petrels and puffins swooping above in a sky often banked in rolling fog. Upon surfacing, her mother would summon Bayla with ascending moos, known as an upcall, until Bayla returned with a swish of her flippers.

On Aug. 27, biologists noted mud on Bayla’s head, a sign of a deep dive — likely a training trip with her mother in the ways of hunting food. Bayla needed to learn well; she was about to enter the most vulnerable period for a right whale. Soon, she would be on her own.

After graduation from Cambridge in 1983, Moore moved to Massachusetts, home of Hannah Clark, a forthright music and biology major at Williams College who had been one of his Newfoundland boat mates. The next year, they married. Hannah took a job teaching music. Moore enrolled in the MIT and Woods Hole Oceanographic Institution joint PhD program in biological oceanography.

To his colleagues, Moore was cordial and persuasive. His craggy face, long and sincere and shadowed by commanding eyebrows, demanded attention when he spoke, which was often in paragraphs. He smoothly politicked through academic logjams, and a reservoir of patience allowed him to maneuver the government bureaucracy that often held the key to funding.

One of his first grants was to study why fish were developing cancer in Boston Harbor. Sewage turned out to be the cause, which led to more research on the pathogenic origin of marine disease. He began showing up at dolphin and whale strandings, looking for samples to collect.

One day, when a whale washed up dead on Cape Cod, Moore arrived with his sample kit. He asked the biologist on site why the animal had died.

“You’re the veterinarian,” said the biologist. “Why don’t you tell me?”

Soon after, Moore began regularly arriving home with a rank smell clinging to his clothes. He had become New England’s default whale coroner, climbing into carcasses up and down the coastline to determine causes of death. Many of the fatalities were right whales. Some had died from ship strikes or disease, but time and again he found the hulking carcasses tangled in fishing rope. He was bewitched by the right whales. They were mega-ton creatures who could dive 600 feet, survive on food the size of a grain of rice and bend their enormous selves to scratch their ears with theirs flukes — and yet, they were regularly succumbing to something so prosaic as fishing rope.

In the fall of 1999, Moore got a call from a NOAA researcher. A team in Lubec, Maine, was trying to cut fishing ropes wrapped around a 10-year-old female right whale. They feared infection had set in where the ropes were cutting her. They wanted to try something new. They wanted him to deliver antibiotics to the whale.

But when Moore arrived in Lubec, he could only watch as a team zigzagged across the water trying to catch up to the distressed right whale. The team tagged her trailing ropes with keggers — buoys meant to slow a whale, similar to the kegs whalers once used to make it easier to close in for the kill. The buoys made the whale thrash harder. The water around her turned frothy white. She was bleeding and vomiting. There would be no getting close enough to deliver antibiotics or disentangle her.

The Coast Guard spotted her a month later off the coast of Cape May. She was hanging below the surface. Once in a while, she tried to breathe, until she didn’t.

Moore was haunted by the encounter. He couldn’t shake the memory of it. The necropsy report turned his stomach: A gill net had sliced a 4.6-foot wide laceration across her back and carved off a swath of blubber as it sawed toward her tail. The gash exposed both her shoulder blades. Each flipper was incised down to the bone; the left flipper had a 5-inch deep cut and the right flipper had one 7 inches deep. X-rays showed the ropes had deformed her bones and altered the way she swam. When examiners cut the rope, a sharp snap could be heard as the tension finally released from the whale’s torso.

Moore felt certain the whale had suffered massive pain. For months, maybe years. The last sighting of the whale before entanglement had been two years earlier, in September 1997. It was beyond what he had imagined. The whale drownings in Bay de Verde cod nets that he remembered had been comparatively painless — over in a matter of minutes. This was something else. This, he thought, was torment.

He was a marine biologist. Getting exercised about animal pain was dangerous terrain; in the scientific community he could be derided as emotional and unempirical. But he was also a veterinarian. He had taken an oath to prevent and relieve animal suffering. Right whales were venturing into waters humans had claimed for fishing, and they were dying, like roadkill. There had to be a way for humans to coexist with the right whales. Surely he could harness science to find a fix.

Bayla and her mother were seen a final time together shortly before noon on Sept. 21, 2009, in the Bay of Fundy. Bayla had scars on her left flipper and tail, evidence of ropes she somehow had given the slip. Luck had been with her.

She departed the bay sometime in the fall and was seen socializing with bottlenose dolphins and three other young right whales off the coast of Florida in February. It’s not clear why Bayla made the trip south since she was too young to be calving.

Then she did another curious thing. She made no appearance in the Bay of Fundy the next summer. Researchers speculate that she went to the summer home of her grandmother — a maverick who slipped the known migratory routines and social patterns of the right whale community to live by her own code, perhaps summering off Iceland.

There’s no real knowing; such is the immensity of the sea and the vastness of what remains unknown about one of the most studied animals in the world.

Figuring out how to stop whales from dying in ropes consumed Moore. Often after dinner with Hannah and the boys, he retreated to his shop, a wood-heated former chicken coop on his island, to theorize.

He wondered if thinner rope might be less injurious, and he directed a student to rig up a machine to test rope widths on blubber. Thinner rope proved more harmful, quicker to cut.

He worked with a Canadian whale biologist to create a model tail, which they used to test a harness they designed. The idea was to wrap the powerful tail of an entangled whale and steady the animal long enough to remove the ropes. In practice, though, the harness didn’t latch.

Moore returned to the idea of antibiotics. Perhaps antibiotics could slow infections from lacerations and give an entangled whale a better chance of survival. He’d had great success measuring the blubber thickness of right whales using pole-mounted ultrasonic probes. Perhaps a pole-mounted syringe and needle could work. But needles proved a different matter. If the syringe failed to release from its holder on the pole, a whale researcher holding the pole could end up attached to an angered whale.

At times, it felt like science was working against him. Chemists were creating ropes with the strength of steel. Fishermen were opting for the stronger ropes because they lasted longer on the rocky ocean floors.

Regulators were attempting to solve the problem. In some areas of Massachusetts where right whales congregated, they had banned the use of certain gear, including crab and lobster pots.

For whales, the hazard was the rope that runs from a floating buoy to a trap on the ocean floor and the underwater rope connecting traps in a long chain. Regulators at the National Oceanographic and Atmospheric Administration ruled that ropes connecting lobster traps had to sink rather than float, making them less dangerous to swimming whales. Sinking ground rope cost three times as much as the floating rope. It also frayed more rapidly and had to be changed more often, adding up tens of thousands of dollars over a decade for a fisherman.

NOAA also ordered that so-called “weak links” be used to connect buoys and fishing ropes so that buoys would detach more easily if a whale got entangled. The regulators said the program was a success, pointing out that right whale numbers had increased from 300 to 450 since regulations were phased in starting in the 1990s.

But to Moore it wasn’t clear the regulations had any impact on entanglement: Right whale deaths from entanglement were on track to double between 2000 and 2014, and the deaths from ropes were getting more gruesome as the ropes got stronger, according to New England Aquarium researchers.

The real answer was off the table. Regulators had decided it wasn’t feasible to get rope out of the water column. There was no way they could prohibit lobstering, not in New England. And they had ruled that gear that could free the ocean from ropes — buoys stored on the ocean floor until released by a timer or acoustic signal — was impractical.

Moore believed the regulators could have been bolder had NOAA not also been mandated to consider the economic well-being of industries like fishing that rely on the ocean. Regulators’ intentions were good. They committed generous funding to researchers studying entanglement. But Moore felt that regulators ultimately were handicapped by having to serve the conflicting interests of whales and fishermen.

Moore’s options were dwindling.

Perhaps the answer lay beyond him, he thought. Maybe it would take the market. Whole Foods could take a cue from Massachusetts. Lobsters caught in state waters were sold with whale-logo-stamped green bands on their claws to show that fishermen had used sinking lines to connect their lobster traps. If fishermen adopted additional and more effective whale-safe techniques, chains like Whole Foods could market lobsters as whale-safe, a kind of fair-trade movement for whales.

But Moore didn’t have a clue about where to begin with that. He was a scientist, not a consumer advocate. He had to focus on what he knew.

He had one more idea.

One day in the middle of winter 2006, Moore picked up his phone and dialed a number halfway around the world.

On Christmas Day in 2010, a Florida Fish and Wildlife aerial team was making a regular survey of right whales. Off the coast of Jacksonville, they spotted a right whale. Visibility was low. But they could see ropes wrapped tightly around it. Rescue teams deployed. Conditions were so bad rescuers could only attach a tracking device to the end of rope trailing the whale so her location could be followed.

Four days later, when the weather cleared, rescuers found the whale thirty miles south in the St. Augustine Inlet. They tried but couldn’t get good cuts on the rope. The next day they sheared a large loop of rope. But the whale was panicked and evasive and wouldn’t let them get close enough to make the critical cuts to the rope in the whale’s mouth that held the complex weave in place.

New Year’s Day passed. The whale swam north to Fernandina Beach. Rescuers noted the whale was dangerously thin.

Word came back from the New England Aquarium. The whale’s markings matched those of a whale in the right whale catalog.

It was Bayla.

Moore liked the voice he heard on the other end of the phone line that day in 2006. Trevor Austin had a matter-of-fact Kiwi delivery. He was an engineer whose company in New Zealand made equipment for tranquilizing animals.

Moore said he had an idea. He wanted to sedate a free-swimming whale so that rescuers could get close enough, for long enough, to remove ropes entangling it. He needed a ballistic system that would send 60 milliliters of sedative flying through the air with enough force to penetrate a whale’s fibrous blubber with a 12-inch needle.

Austin was silent. The largest-capacity animal syringe held a tenth of what Moore wanted.

“We’ll give it a go,” Austin said.

Moore sent him $25,000 that NOAA had supplied for the project. A year later, on a raw March day, Austin arrived at Logan Airport carrying a black Pelican case packed with anodized aluminum tube syringes, stainless steel needles, and a dart rifle.

Moore and Austin drove to a range on the Cape. Moore had a cooler with three squares of dolphin blubber. Tacked together, they measured the same depth as a right whale’s. Moore perched the blubber against a hay bale.

Austin took a shot. A blank .22 cartridge sent the dart exploding out of the chamber. The dart bounced off the blubber.

Like a bullet-proof vest, Austin thought.

Austin fired again. This time, the dart entered the blubber but promptly bent in half. Austin and Moore huddled. The syringe’s momentum had continued after the needle entered the blubber, taking the needle along and bending it. The needle needed more resilience. They retreated to Moore’s lab at Woods Hole and glued a carbon fiber tube to the needle’s stainless steel husk.

The next day, they drove back to the range. Austin took a shot. A perfect strike.

Moore got a live test case six months later. A mother and calf humpback had gone astray on their migration north and swam 90 miles inland in the Sacramento River Delta, through three bays and past five bridges. They had wounds, likely from a ship’s propeller, and the fresh water was degrading their skin. They needed antibiotics. Moore was called out to California. He loaded the medications into the dart rifle’s syringe. A colleague aimed and fired. Within a week, the whales, successfully treated, had regained enough strength to make their way back to the open ocean.

Moore had his device.

On a January day in 2011, Moore was sitting in his office at Woods Hole when the e-mail arrived. Was he available to sedate the calf of Picasso? Yes, he replied. He was on his way.

In a hotel room in New Smyrna, Moore and the fleet of biologists from across Florida, Georgia, and Massachusetts reviewed the details of the operation. The meeting went long and sleep was short, but the next morning, Moore’s mind whirred with possibility as the radio of the overhead airplane reported Bayla was surfacing.

Bayla’s back glistened as it moved across the waterline on the January morning, a black sheath divided by the ropes leading out of her mouth.

The man standing next to Moore on the tower of the Zodiac cocked the dart rifle tipped with the sedative-filled syringe. “We’re live,” Jamison Smith said. Moore was a good shot, but Smith, who helped direct the federal effort to stop whale entanglements, was better. He’d grown up hunting ducks and other waterfowl with four brothers in Florida.

Don’t miss, Moore thought as he gave the command to shoot.

The report was a sharp crack. A splash erupted at the waterline next to Bayla’s torso. An orange buoy tied to the syringe for tracking fell to the water. The buoy jerked, then began moving. The dart was traveling with Bayla.

“The f---ing thing worked,” Moore said, his voice rising and surrendering to surprised wonder.

The radio erupted with excited chatter from the other boats and the overhead plane. As they tracked Bayla diving and surfacing, then diving and surfacing again, elation bubbled. The sedative hadn’t killed her. But there was work yet to do. “Back away,” Moore called to the driver of his boat.

The clock was ticking. The sedation would last 90 minutes.

Soon a more nimble inflatable craft moved in.

The boat was piloted by Chris Slay, a Georgia biologist and motorcycle racer. Mark Dodd, a life-long surfer and another Georgia biologist, held a carbon-fiber pole fitted with a knife that Slay had designed for cutting tight entanglements like Bayla’s. Instead of a traditional hook that slid under the rope to make a cut, a spring-loaded mechanism sent a blade plunging at the rope from above. Dodd was on his knees, scooted into the bow, like the nose gunner of a B-17.

Dodd and Slay were old hands at freeing whales from ropes. They had pursued entangled whales up and down the Georgia and Florida coasts, at times, only to have the whales disappear before they could get a single cut.

Slay motored behind Bayla, guided by two beach-ball-sized orange buoys that had been attached to her trailing fishing ropes that morning. Her pace and cadence had to be understood before the chase could begin. What Slay saw astonished him. Bayla was swimming in a straight line. None of the sharp turns he was used to with right whales dodging rescuers. Every five minutes she came up to breathe. No deep, unpredictable dives.

She was a perfect target. She was theirs to lose.

Slay gave Dodd the signal. As Bayla surfaced, Slay gunned the motor, closing the distance between Bayla and the boat. Dodd punched the ropes with the knife but the ropes didn’t give. Slay backed the boat off. They tried again. Another miss.

Something was misaligned, Dodd shouted over the whine of the engine. They couldn’t afford another flawed rally. “I’m not sure anything was cut. Honestly, I’m not sure.”

“Focus as much as you can on exactly where you want to hit it,” Slay said.

The aerial team radioed. Bayla was rising. Dodd leaned over the gunwale. He could see a shadow a few meters off the right bow. “Her bonnet’s right there! She’s coming up. See it right there, Chris?”

Slay opened the throttle. The boat clipped right. Dodd hoisted the knife. Bayla’s head emerged and water cascaded down her sides. A spangled spray of phlegmy blow blasted Dodd’s eyes and nose.

Fundamentals, Dodd thought.

He pictured the matrix of ropes, their loops and twists. As the spray cleared, the ropes appeared and were level with his face. He heaved forward with a grunt and thrust the pole.

If Bayla felt anything, she gave no indication. But before the force of the strike repelled him to the floor of the boat, Dodd glimpsed the ropes slacken.

Slay whipped his head around. Two orange balls bobbed in place behind the boat.

“The buoys are dead in the water,” Slay said.

The ropes had fallen free.

As the sun descended, the inflatables steered into harbor. Fatigue was settling. There would be time later for the team to deconstruct the day’s success, but Moore needed to know one thing. He approached Slay.

“Did the sedation make a difference?” Moore asked.

Slay smiled. “Hell yes.”

For six days, Moore’s e-mail pinged with daily updates on Bayla’s coordinates as she swam south down the Florida coast. The information came from a temporary satellite tag that the disentangling team had attached.

Then, as planned, the tag had fallen away and Moore’s e-mail had gone dark with news of Bayla.

Her whereabouts were unknown.

On Feb. 1, Moore leaned against the office doorway of his graduate student, Julie van der Hoop. “There’s a dead whale in Florida,” he said.

She had followed the news of Bayla like everyone in the right whale community, asking Moore each morning if another ping of her coordinates had come in. Her face darkened.

“Is it the calf?” van der Hoop asked.

“I don’t know,” Moore said. “There’s a necropsy scheduled. Do you want to come?”

Moore and van der Hoop arrived in St. Augustine the next day. The following morning, they watched as the sun rose over a young right whale beached on the sand.

She had a black chin.

A team of researchers cut away Bayla’s shark-mauled blubber with long knives and examined her internal organs. In her mouth, they discovered rope that Dodd and Slay hadn’t gotten. It was so deeply embedded, new tissue had grown over it, “like a pig in a blanket,” van der Hoop would later observe in her journal.

By day’s end, the team determined that Bayla had died from severe emaciation and lacerations caused by hundreds of feet of 7/16-inch diameter floating polypropylene rope that connected traps or pots — the sort that NOAA had attempted to restrict.

Beyond that, there wasn’t any more to be known. The rope could have come from off the coast of New England, or perhaps Canada; by the time Moore’s team had cut it away, she was too weakened to survive.

There would be no decorous burial for Bayla; her size defied it. An excavator scooped her muscle and soft tissues into a hole dug in the mucky sand. The loader then piled Bayla’s bones onto a truck destined for Atlanta, where her skeleton would be reassembled for display at the Georgia Aquarium and she would be given the Hebrew name Bayla, meaning beautiful.

When the work was done, Moore held a needle. It was the needle that researchers had fired from the rifle to deliver antibiotics to Bayla after her sedation. It was bent at an 80-degree angle. He suspected it had caused Bayla more pain. There were lessons to be learned from why it bent. He would write a paper. His peers would review it. A journal would publish it.

But that was for another day.

For now, Moore cried.

The needle sat on his desk for a year taunting him.

The paper was hard to write. Harder than any other. When it was done, there was relief. But the relief soon was replaced by creeping doubt.

A colleague e-mailed him thanking him for his efforts to save the right whales from entanglement. Moore replied that he wasn’t sure the thanks was due. He still had no solution. After all these years, he still didn’t get it.

A bleak realization had settled, he wrote. “I’ve failed.”

The winds in the Bay of Fundy were steady and Moore hoisted the mainsail of the Rosita, the sailboat he and Hannah named for a whaling station in the South Atlantic that had been planned but never built. Moore liked to think of the Rosita as embodying the spirit of whales spared the harpoon.

Every few minutes, Moore whipped his head right or left, drawn by the chuff of spouting water. Grand Manan Island spread across the western horizon. Ahead, right whales lolled at the waterline, breathing hard after what must have been deep dives for food. There were dozens of right whales in the Bay.

Almost to a one, they had fishing rope scars.

Moore and Hannah were at the end of a summer vacation. It was August 2014, more than three years since Bayla’s death. He had continued whale research but often felt he was going through the motions. He was due back in the office at Woods Hole in a few days, but not certain of what he was returning to do.

Over vacation, an idea had begun swatting at him, one his younger self would have considered heresy. Science had been superb at documenting the problem of entanglement. But science had not been good at finding a solution to end it.

How many papers had he written? How many necropsies had he performed? How many ideas had led nowhere?

Sedation had proved workable, but inevitably came too late for whales like Bayla. Moore and others had concluded prevention was the only answer in cases like hers.

There were new regulations coming online. Fishermen soon would have to attach a minimum number of traps to a buoy line and they would have to better mark their ropes. And the areas in Massachusetts where right whales congregated were to be closed to gear such as traps and pots for longer periods.

But fishermen were protesting, and NOAA was revisiting some of the new rules.

Moore always thought that if dogs walked around the city of Boston with bleeding lacerations, people would become outraged and demand that the source of injury be stopped.

Whales swam unseen with their wounds.

He was 57. Retirement was approaching. But there was time yet.

Maybe if he could communicate what he had felt all those years ago. If people could feel what he felt when he heard the whales singing in his dreams, maybe then they would come to share his heartache, and wake to the need to do more.

Mist spouted in front of the Rosita. Moore climbed onto the prow. Sun was splintering through the clouds and the slanted rays met the water in bangles of light. Somewhere out there Picasso swam. Aquarium researchers had spotted her in the Bay. Perhaps she was the right whale in front of him, dunking its head and driving its tail into the air until it was perpendicular with the surface, like a salute to the terrestrial world.

“There’s something about a right whale’s tail that’s just gorgeous,” Moore mused. “Michelangelo could have sculpted it.”

Moore rested his body against the mast. The ocean spanned before him.

“We’re surrounded by right whales,” he said.

Another view The story of Dr. Moore and Bayla, in photos, videos, and sound. Click for visual view

Sarah Schweitzer can be reached at sarah.schweitzer@globe.com.

About this story: Scenes of the attempt to save Bayla were based on extensive video footage taken by helmet cameras worn by Moore and other rescuers during the operations. Dialogue in other scenes was recreated from first-hand accounts.