Removing a thick fishing rope from a highly fertile whale’s jaw was a priority for scientists who fear the species may be in terminal decline

A mission to disentangle a particularly important North Atlantic right whale from a thick rope wrapped around its jaw has proved a partial success, amid growing fears that the endangered species is approaching a terminal decline.

The individual female whale, known as Kleenex, is considered one of the most productive North Atlantic right whales left in existence, having given birth to eight calves. Its condition has deteriorated, however, since it was spotted off the coast of Delaware in 2014 with a thick fishing rope wrapped around its head and upper jaw.

Conservationists, aware that the right whale population has dropped alarmingly due to a spike in deaths and a birth drought, attempted to remove the rope last week, after Kleenex was seen near the Massachusetts coast. A pursuing team used a crossbow to fire a bolt with razor blades attached at the rope, but did not successfully sever it.

“The line was damaged and then the whale became more evasive and the weather got worse, so that was our best go at it,” said Bob Lynch, of conservation group Center for Coastal Studies, who was part of the rescue team.

North Atlantic right whales may face extinction after no new births recorded Read more

“Ideally you’d get them on a table for a surgery but you can’t really do that with a whale. We deteriorated the quality of the line so hopefully it will help it break up over time. Whether that will be enough for this individual is hard to say, though.”

Kleenex is still able to feed but has lost weight, limiting her ability to have another calf. No new right whales were born off the south-east US coast over the winter calving season, the National Oceanic and Atmospheric Administration confirmed, meaning that the fate of even a single prodigious reproducer like Kleenex, thought to be aged around 50, could be crucial to the fate of the species.

“She is a rockstar of reproductive females and the species cannot afford to lose her,” said Heather Pettis, a scientist at the New England Aquarium.

“If the current rate of mortality continues, we will lose all reproductive females within the next 23 years, at which point the species is functionally extinct. If the line breaks up and she is free, she will be able to build up fat reserves and produce more calves in the future.”

The confirmation that no known calves were born over the winter is a blow to a species that is now thought to have a population of fewer than 450. “It’s the worst scenario we could’ve pictured, given it’s on the heels of a devastating series of mortalities,” Pettis said.

Facebook Twitter Pinterest The world population of North Atlantic right whales is believed to be fewer than 450. Photograph: Michael Dwyer/AP

Scientists suspect that females are unable to put on enough weight to become pregnant, causing the birth rate to plummet. The feeding problems could, in part, be due to an increase in entanglements with more durable types of rope than those the whales were previously able to break.

The whales are also altering their range, most likely because their plankton food base is shifting. This has brought the species into areas dotted with fishing boats and other shipping off the north-eastern US and Canada, leading to entanglements and ship strikes. Last year, the Canadian government introduced stricter speed limits in the Gulf of St Lawrence for vessels measuring more than 20m, to prevent more whale deaths.

North Atlantic right whales have gone through years of lean birth rates before, such as in the late 1990s and early 2000s, and managed to bounce back. The species was nearly hunted to extinction before conservation efforts helped reverse its fortunes.

However, scientists warn that the current low birthrate is a major concern given that it is combined with an increase in mortalities, a situation that presents a significant risk to the species.

“I’m very concerned, the species isn’t in a good place at the moment,” said Mark Baumgartner, a marine ecologist at the Woods Hole Oceanographic Institution in Massachusetts.

“But we have it in our power to change our activities so right whales can thrive in our oceans. We can have profitable shipping and fishing industries and still have right whales.”