Emily Chan
Between 2012 and 2021, the number of humpback whales in the North Pacific Ocean experienced a decline of 20 percent, likely from a massive marine heat wave that began in 2013 and lasted until 2016.
Over the last two decades, a team of researchers has been tracking the population trends of the species.
In 1986, the International Whaling Commission implemented a moratorium on commercial whaling, helping humpback whales bounce back from the brink of extinction. The whaling ban remains in place today.
The researchers believed that the number of humpback whales would have grown even more since then, but to their surprise, they found that the whale population had actually dropped.
From 2002 to 2012, humpback whales in the North Pacific Ocean went from 16,875 to 33,488. But then, between 2012 and 2021, only 26,662 humpbacks were left alive.
These findings suggest that the marine heat wave of 2013 to 2016, sometimes known as “the blob,” is to blame for the sharp decline. It was the largest one ever recorded in the world.
During this period, the ocean temperatures were four to 10 degrees Fahrenheit higher than usual, causing around 7,000 whales to starve to death.
The event contributed to the loss of resources. More marine animals were competing for food that was less available. Zooplankton became less nutritious, which meant that fish were smaller. Humpback whales depend on those fish for food, but they aren’t getting enough calories from them because of the marine heat wave.
The whales became thinner, more susceptible to contracting disease, and less likely to reproduce. Fewer whales and calves were spotted at breeding grounds during that time.
Sign up for Chip Chick’s newsletter and get stories like this delivered to your inbox.
