North Atlantic right whales are now generally less bulky and shorter than they once were, with some individuals experiencing an extreme decrease from previous standards. “There are outliers that are about 3 meters shorter, which was really striking to see,” said Joshua Stewart, marine researcher with the National Oceanic and Atmospheric Administration (Noaa).

“I saw pictures of 10 year old whales the size of two year old whales, which was shocking. They are very small, stunted whales, ”added Stewart.

Stewart, along with colleagues from Noaa, the New England Aquarium, Oregon State University, and the Woods Hole Oceanographic Institution, used a multitude of aerial images taken of whales from manned planes and drones to distance over the past 20 years to estimate the length of right whales. .

Researchers were able to closely follow the growth of individual whales by identifying them from distinctive patterns on their heads. North Atlantic right whales are among the most studied whales in the world, with only around 400 cetaceans in the wild.

The study, published in Current Biology, suggests that whales suffer long-term intergenerational damage from being trapped in fishing nets and lines set to catch other species. Fishing gear undermines the strength of whales, preventing them from using their energy to pile on weight and length. Whales are also at risk of being struck by ships on the busy North Atlantic shipping lanes.

“If you drag fishing gear you have less energy to grow taller, that’s a pretty clear mechanism,” said Stewart, “If I tied a sandbag to you and asked you to walk a lot, you would get skinny. fairly quickly. For whales that also means that they can also produce smaller calves which have lower probabilities of survival. We are seeing a long-term decline in their size. “

The species got its name from the fact that it was the “right whale” to target for whalers due to their slow speed and penchant for feeding on plankton on the ocean surface. Whaling may be over now, but whales suffer from other man-made threats in the Atlantic, such as ship strikes and entanglements, as the warming ocean returns their prey more difficult to find.

Last year, the International Union for the Conservation of Nature announced that the species was one step away from extinction, raising its classification from “endangered” to “critically endangered”. extinction “. According to the IUCN, of the 30 deaths or serious injuries of North Atlantic right whales recorded between 2012 and 2016, 26 were caused by entanglement of fishing gear.

The fishing industry has raised concerns about the cost of upgrading gear to avoid right whale entanglements, but scientists say immediate action is needed to prevent the species from being completely annihilated.

“Implementing proven solutions such as reduced vessel speed, lower breaking strength ropes and cordless fishing gear more widely across their range are critical and urgent steps needed to avoid ‘extinction of this species,’ said Amy Knowlton, co-author of the new study and scientist at the New England Aquarium in Boston.