There was a time not so long ago when trained observers were overwhelmed by the number of whales migrating through Monterey Bay.
In 2016,“we had times when there were so many whales in front of us that it was difficult to count them all,” said Aimée R. Lang, research biologist at NOAA’s Southwest Fisheries Science Center.
Not so much anymore.
Whale experts are anxiously awaiting the 2024 count, which could hold more bad news about migratory gray whales, whose population has been declining.
Last year’s gray whale count showed a sharp decline, a negative trend consistent with the past few years. The count could be low for plenty of reasons and none in isolation. It might be that the whales are migrating farther offshore, out of sight of the cliff-side counters. It’s possible the whales are delaying their migration to gain a little more winter weight. Or maybe, the population peaked too high, and the numbers are dropping to a level the waters along the Pacific coast can sustain.
Gray whales were the original “whale-watching whales.” The first-ever water-based whale watch in the United States took place in 1955 at Cabrillo National Monument in San Diego, when whale-spotting hopefuls paid $1 to catch some gray whale tail flips. In the 1960s and ‘70s, California fishermen often forfeited the off-season catch to profit from whale-watching tours during the winter, when the charismatic creatures make their 6,000-mile journey from their Arctic feeding grounds to give birth in the calm, protective lagoons of Mexico.
After they were nearly hunted to extinction by commercial whalers, gray whales were federally protected by the Marine Mammal Protection Act in 1972. From then on, the eastern gray whale population experienced turbulent but steady population growth and peaked in 2016 at 27,000. In 2023, the whale counters estimated the population at 14,500 — around the same abundance as when they were recovering from commercial whaling.
One fish, two fish
How do we know how many whales pass the bay? Binoculars and patience.
“It’s actually pretty simple. We have a team of two observers scanning the study area by eye and with binoculars, counting the whales as they go past,” said Lang, the research biologist at NOAA’s Southwest Fisheries Science Center.
The team starts their survey at the end of December and watches until mid-February. At the end of the field season, they surmise how many whales likely swam past at night based on the day counts. During the northbound migration in the spring, counters specifically look for mother-calf pairs.
After the high 2016 count, NOAA did another survey in 2019. That year, the whale counters identified fewer animals. By the end of 2019, over 200 whales had stranded along the Pacific coast, which triggered the declaration of an Unusual Mortality Event (UME).
The population was down, and the remaining individuals were struggling.
“I’ll never forget in the 2019-2020 season, they were coming down from their feeding grounds, and they were very thin on the southbound migration,” said Colleen Talty, marine biologist at Monterey Bay Whale Watch. “Usually, we see thin whales on the Northbound migration because they’ve already fasted for four months. So that was super concerning.”
Instead of fat and happy whales bypassing San Francisco Bay to keep on toward Mexico, they were pitstopping in the Bay to feed on krill. “Basically, they were starving, so they were getting hit by boats more often because the shipping community wasn’t used to the gray whales going inside the Bay,” said Talty.
A January report by volunteers off the Palos Verdes Peninsula Coast indicated a 40-year low for the southbound population. Until the NOAA’s Southwest Fisheries Science Center’s official population count this winter, we won’t have a full picture of the current population. But there are a few potential reasons for this overall population decline.
Usually, gray whales come in close to the coast to avoid crossing over deeper waters, prime habitat for their predators. Whale counters can watch for “blows” — clouds of water vapor that indicate a whale’s exhale. But starvation might be encouraging shortcuts, so the whales might be traveling too far offshore for the counters to see. “Most likely, they’re taking a shorter route to get down to Mexico rather than the coastline. It cuts down on several hundred miles in the long run,” said Talty.
Gray whales spend the summer eating in Alaska. They feed on amphipods, tiny crustaceans that eat algae off the underside of northern sea ice. As temperatures warm due to human-caused climate change, sea ice melts. Without a place for their food to grow, amphipods starve, so whales suffer, too.
Gray whales are known to fast during their migration, so ideally, they begin their journey with lots of winter weight. With a dwindling food supply, they might be starting their migration later to gain more winter weight.
“Over the last four or five years now, we’ve noticed it’s about three to four weeks delayed. They seem to be spending more time up in the feeding grounds before heading down to the breeding grounds in general,” said Talty.
It could also be that the gray whale population has reached carrying capacity—the number of individuals an environment can support. It’s possible that their 2016 abundance tipped the balance, and the Pacific coast simply can’t feed that many whales. But while carrying capacity is considered a natural limit, climate change is impacting it in an unnatural way, according to an October 2023 study published in Science.
But it’s not all bad news. Last year, there were fewer strandings in California and Mexico than in any year since 2019. Also, the 2023 calf count in the lagoons in Mexico was the highest in five years, which suggests a growing population.
It’s too soon to make a call about the status of the population, but so far in the 2024 migration season, NOAA’s raw whale counts are similar to, but slightly higher than they were last year at this time.
“We don’t know how that is going to translate to our abundance counts,” Lang said, “without doing all the math.”