Why North Atlantic right whales are now smaller than 40 years ago
The North Atlantic right whales seem to be shrinking: their average length today is one metre shorter than the same species of whales in the 1980s.
Some whales are three meters smaller than their predecessors.
From this perspective, some 10-year-old whales today only grow to the size of one or two-year-old whales 40 years ago.
This is the discovery of a recent study of decades of data. This is another blow to the endangered species, and it has been struggling to survive.Despite the efforts of Canada and the United States, fewer than 400 whales currently number are trapped in fishing gear or killed after being struck by ships every year. Government intervention.
“I was very shocked,” said Joshua Stewart, a research assistant at the National Oceanic and Atmospheric Administration and lead author of the paper. Appeared in contemporary biology, A peer-reviewed journal.
When field biologists photographed calves that they thought were one year old based on their size, Stewart began to study the topic, only to realize that the whale was actually 5 to 10 years old.
Watch | Reasons for the decrease in the number of right whales:
With the help of various other researchers and biologists, Stewart collected as much data as possible on the size of whales dating back to the early 1980s.
“This data was collected before I was born,” he said in Mexico, where he currently works.
In this study, the researchers compared aerial photos taken decades ago with the most recent Drone shooting. Detailed notes and measurements taken by field biologists dating back to the 1980s also proved to be vital to their work.
After the study was completed, the size difference became obvious.
The possible culprit? The whale was caught by fishing gear.
Stewart said: “The most important thing we found is that whales with prolonged tangles that last for months or years are slower than whales that are not tangled.”
Most North Atlantic right whales are trapped by fishing nets and traps at some point in their lives.
The paper’s co-author and senior scientist at the Anderson Cabot Ocean Center, Emino Knollton, said: “More than 85% of the population has tangled injuries, whether it is scars or attached equipment, so this is a big deal for this group. Quite a long-term problem.” Living in Cambridge, Massachusetts.
After spending several years documenting whale entanglement, Knowlton contributed entanglement data to this research.
The toll caught by nets and ropes is extremely destructive to the whale’s body and often leads to its death.
Stewart said: “You can imagine if we tie you a sandbag, you have to drag it for months or a year.” “You will put much less energy into other things, especially if you It’s still growing. You may be stunted by dragging a sandbag around and burning too much energy.”
Stewart said that other whale species that are frequently trapped are likely to be experiencing similar size reductions. But because North Atlantic right whales have long been on the brink of extinction, they are one of the few species with detailed data sets dating back decades, and researchers can use it to prove this.
It’s not just that mature whales caught by fishing gear are getting smaller and smaller.
According to this study, baby whales whose mothers are entangled are also more likely to be stunted.
That’s because troubled mothers are also struggling to produce milk and feed their children. The energy spent to survive will consume the energy originally used to produce milk.
Knowlton said: “For a seriously injured woman, she also needs to recover from these injuries, which will transfer energy to take care of her calf so she can try to heal and survive.”
According to Knowlton, fishing with weaker ropes will give whales a better chance of freedom. Even better is to get rid of the rope altogether, Use cordless traps, First of all, you can prevent whales from being caught.
Both scientists believe that if the whale has a chance to regain its species, it will eventually return to its normal size.