WILLIAM BRANGHAM: Spotting some right whales off the East Coast of North America can be a majestic site.

But those whales are endangered and their numbers are shrinking.

Many conservationists say fishing gear that entangles these mammals is a big part of the problem.

But lobstermen now fear they may be driven out of business if they're pressured to change their practices even more.

Science correspondent Miles O'Brien reports on a battle that both sides say is existential.

MILES O'BRIEN: Steve Train has been fishing the waters of Casco Bay, Maine for 49 years.

STEVE TRAIN, Commercial Fisherman: It's a way of life for the people from the time they're born.

MILES O'BRIEN: His home is on an island four miles northeast of downtown Portland.

It's a community built on lobsters, like so many here in Maine.

STEVE TRAIN: It provides for a lot of other things.

Lobster is what's maintaining more than summer communities in most of these peninsulas and islands.

MILES O'BRIEN: Lobsters support about 15,000 jobs and contribute more than a billion dollars to the Maine economy.

And yet the industry sees itself in an existential battle, pitted against a rare species fighting its own existential battle.

North Atlantic right whales, critically endangered, fewer than 350 individuals remain.

And they are dying at a devastating rate.

JANET COIT, Assistant Administrator of Fisheries, National Oceanic and Atmospheric Administration: If we don't stabilize and begin the recovery, they will be gone within a couple of decades.

They will be extinct.

They will be wiped off this Earth.

And we want to do everything we can to prevent that from happening.

MILES O'BRIEN: Janet Coit is the assistant administrator of fisheries at the National Oceanic and Atmospheric Administration, NOAA.

How many mortalities a year are acceptable, in your view?

JANET COIT: Zero.

If we have a human-caused mortality of even one whale a year, we're losing ground.

MILES O'BRIEN: So what is killing them with such alarming efficiency?

In the past six years, vessel strikes have killed 12, an entanglement with fishing gear has killed nine and injured 66 others.

As the whales migrate along the Eastern Seaboard, they swim through a fast-moving armada of boat and ship traffic and a manmade underwater kelp forest of vertical ropes, fishing gear.

Maine alone sells permits for about 2.8 million lobster traps per year.

The traps sit on the bottom, three to 20 of them linked in a daisy chain known as a trawl.

Tens of thousands of vertical lines connect the trawls to buoys that dot the surface.

In 2021, NOAA finalized regulations to reduce all that rope dangling in the water, mandate gear marking, and add weak points that whales can break through.

It also called for a seasonal lobster fishing closure of 1,000 square mile area of the Gulf of Maine.

JANET COIT: I think a goal that we all share is to have more monitoring, so we can have more dynamic regulation.

But, right now, we have to take a broader approach to try to reduce the risks that are killing whales.

MILES O'BRIEN: The regulations are based on an algorithmic prediction of the risk to the whales in these heavily fished waters.

But the lobster industry insists it is not proven guilty.

PATRICE MCCARRON, Maine Lobstermen's Association: They are assuming the absolute worst-case scenario, and it is nothing that is reasonably certain to occur.

MILES O'BRIEN: Patrice McCarron is policy director for the Maine Lobstermen's Association.

PATRICE MCCARRON: Our concern is, the amount of risk that they're saying we're responsible for doesn't match the data.

We have no right whale deaths attributed to the Maine lobster fishery ever, the last known entanglement, 2004.

MILES O'BRIEN: But researchers believe they only document a third of right whale deaths.

And what's more, linking entanglement injuries and deaths to a specific culprit is a huge challenge.

JANET COIT: We have documentation that North Atlantic right whales are in the Gulf of Maine, but because gear wasn't marked and because it's often hard to retrieve the gear, we can't say with certainty where that gear came from.

Only 1 percent of the entanglements that we have been able to document do we know where that gear has come from.

MILES O'BRIEN: In 2020, Maine lobstermen started using lines with distinct purple strands.

Gear marked this way has entangled humpbacks and minkes, but, so far, none has been found on right whales.

STEVE TRAIN: We're getting blamed for something that nobody can prove we're doing.

It would be like saying we know people are speeding, so anyone who's got a car that does over 80 miles an hour, we're going to write a ticket for it.

If it's not us, it's not us.

MILES O'BRIEN: Nevertheless, Maine lobstermen are now using rope that has weak links, so that whales can break though.

STEVE TRAIN: You can use a little piece of plastic that's got little weaknesses in it and tie it, spliced into it, or you can use a weak rope.

MILES O'BRIEN: And this is weaker, huh?

STEVE TRAIN: This is weaker.

It's the way it's made.

MILES O'BRIEN: The Lobstermen's Association says it has done enough and has sued the government to stop further regulation.

In June, a federal judge ruled in their favor, writing that NOAA Fisheries is indulging in worst-case scenarios and pessimistic assumptions to benefit a favored side.

Six months before that court ruling, the Maine congressional delegation flexed its claws on behalf of one of its largest industries.

SEN. ANGUS KING (I-ME): Why am I here to discuss lobsters on the floor of the U.S. Senate?

MILES O'BRIEN: Senator Angus King led the effort to insert a rider in the federal omnibus spending bill to buy some time, a six-year delay on imposing the new regulations.

SEN. ANGUS KING: One, two.

It's counting down.

MILES O'BRIEN: The reprieve came with money to research better ways to track the whales as they migrate and develop fishing techniques that don't require vertical ropes dangling in the water.

MAN: Press and release.

MILES O'BRIEN: That idea is not just hot air.

This inflatable ballistic nylon bag might be a solution.

A select few lobstermen are beta-testing so-called on-demand lobster traps.

ROB MARTIN, Commercial Fisherman: I can see my gear anywhere in the world.

MILES O'BRIEN: Rob Martin's home port is Sandwich, Massachusetts.

ROB MARTIN: It's like anything.

Once you do it a while, it's second nature.

MILES O'BRIEN: An acoustic signal with a unique code activates the air tanks linked to the lobster traps on the bottom.

MAN: Now ready to deploy.

MILES O'BRIEN: Releasing compressed air into a tethered bag, sending it to the surface.

The vertical rope is only in the water as long as it takes to retrieve the attached traps.

MAN: We need a bigger boat.

(LAUGHTER) MILES O'BRIEN: The nascent technology allowed Martin to fish for lobsters this year in Massachusetts waters closed to protect migrating right whales.

ROB MARTIN: This takes a few minutes more to haul the gear, but a few minutes more to haul the gear or stay home.

It's not for everybody.

I always tell guys, this is to get you back into a closed area, and it's another tool in your toolbox if you get closed.

MILES O'BRIEN: But, as it stands, right whales are speeding toward extinction.

The clock is ticking on a majestic species and an iconic industry.

For the "PBS NewsHour," I'm Miles O'Brien off Sandwich, Massachusetts.