New count of gray whales along West Coast suggests rebound

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A new count of the gray whale population along the West Coast shows “signs of recovery” five years after hundreds of them washed ashore and the population began declining, according to the National Oceanic and Atmospheric Administration.

Scientists estimate the total number of eastern north Pacific Gray whales to be somewhere between 17,400 and 21,300, an increase from last year’s estimate, which had shown another year of decline. Last season, scientists estimated between 13,200 and 15,960 whales.

“It’s nice to be able to report some good news the last couple of years,” said Aimee Lang, a research biologist with NOAA’s Southwest Fisheries Science Center.

There had been hints that the population might be starting to recover as researchers last year saw fewer skinny gray whales, more mothers with their calves and fewer dead whales washed ashore, Lang said.

Now the new population estimates are the latest sign things might be trending in the right direction for the intrepid species.

NOAA has determined the “unusual mortality event” for the gray whales that began in 2019 is over. The population had been in decline since reaching a peak in 2016 with an estimated 26,960 whales.

Scientists use a statistical analysis to estimate a range on counts of migrating whales just south of Monterrey Bay, where a deep-water canyon runs close to shore, she said. The model accounts for uncertainty in the counting process, like when observers miss whales due to poor weather conditions or it being nighttime, though researchers are experimenting with also using drones to count whales, Lang said.

Generally, the eastern north Pacific Gray whale population are surveyed for two consecutive years out of every five years, Lang said. With the mortality event designation, the gray whales along the West Coast had been surveyed every year since 2019, aside from the 2020 to 2021 season due to the pandemic, she said.

For a while scientists have been unsure whether the population fluctuations have been due to natural cycles of adjusting for overpopulation or due to other factors, but recent research has pointed to conditions in the Arctic as a possible explanation.

A study from last year found a relationship between gray whale populations, sea ice cover and how much prey was available in the Arctic, where the whales spend their summers. Sea ice can affect whether the gray whales are able to swim down to the bottom and “take big gulps of sediment” to sift for tiny crustaceans, NOAA spokesperson Michael Milstein said.

So does that mean that melting arctic sea ice might be good for the gray whales? It’s more complicated than that, Lang said.

“As we move into the future, the declines in sea ice are probably going to have other environmental impacts and we don’t truly know how that’s going to impact gray whales,” she said.

The eastern north Pacific gray whale is considered a conservation success story and their population has broadly rebounded since they were protected under the Marine Mammal Protection Act in 1972. They neared extinction in the 1950s due to commercial hunting but were removed from the endangered species list in 1994. Since then, scientists have regarded their fluctuations in population to be a part of a normal process.

The species completes a marathon migration each year, traveling nearly 10,000 miles between the Arctic and Mexico, where the whales spend time in lagoons, raising calves. A group of the whales that stops in Puget Sound to feed on ghost shrimp burrowed in mud flats have been fondly called “the Sounders.”

Lang is working on counting the number of mother calf pairs of gray whales that pass an area near Big Sur on their northward migration.