Three pairs of binoculars poke out between baseball caps and balaclavas in the middle of the Gulf of California.
A trio of Mexican scientists are looking toward the watery blue horizon for clues. Sperm whales haven’t been spotted here for years, and fin whales and dolphins aren’t as plentiful. Those that do turn up are more likely to appear malnourished or ill.
This vital ecosystem is struggling, scientists say, if Earth’s largest living creatures are any indication.
“Marine mammals, and specifically cetaceans, are considered the sentinels of health of the marine ecosystem,” said Hector Pérez Puig. He studies cetaceans, the broad category that includes whales and dolphins, at the Prescott College Kino Bay Center in Bahía de Kino on the Sonoran coast.
Pérez Puig, who’s made weekly outings in the gulf since 2009, works with his colleagues to document the health of this ecosystem by tracking population sizes and whale behaviors.
Suddenly, their small fishing skiff jets off in the direction of a distant plume of mist.
“That’s what’s know as ‘el soplo,’” Pérez Puig said, motioning toward a far-off exhalation of a huge, surfacing fin whale. “It means showtime for us.”
The boat catches up to a group of fin whales on the move. Their backs break the surface like the rising humps of giant sea snakes. The researchers chat excitedly while they snap pictures of the animals’ pointed dorsal fins. Each fin is unique, like a finger print. The scientists' main mission is to catalogue each whale’s location — and the conditions where they spotted it.
From there, they extract hints on how the population of these fin whales, and other marine mammals in the gulf, are changing.
The number of fin whales in the area is declining, Pérez Puig says. The ones they do see are more likely to look emaciated than when he started these outings 16 years ago.
“That’s an indicator that probably something happened in the marine ecosystems,” Pérez Puig said.
Their population includes a resident group that permanently calls the gulf their home. It’s one of the only groups of fin whales in the world that stays in one place, rather than migrating seasonally, making the viability of this area even more important.
Sperm whales used to roam these waters, too, but the last sighting was over five years ago. That spotting was already an anomaly, Pérez Puig says. The giant, toothed mammals — the inspiration for Moby Dick — were once common here.
Why they left and where they went is another mystery Pérez Puig and his team are trying to solve. There are a few things they do know for sure. For one, the sea surface temperature in the Gulf of California has increased due to climate change.
Overfishing is also playing a role. Pérez Puig published a paper in 2024 showing the sperm whales’ disappearance collided with a dramatic plunge in the commercial squid catch. The animals are sperm whales’ main food source.
“We know that in the Gulf of California, that fishery has collapsed,” Pérez Puig said.
Whales act as sort of a thermometer, he says. Disturbances in their food supply can have big impacts on where and how they’re spotted.
What the whales are trying to tell us about the health of this place is important for the many other species — and industries — that call this body of water home. The sheltered waters of the Gulf of California nurture an enormously diverse ecosystem. Some of those species can’t survive anywhere else. Others, like shrimp and sardines, represent important harvests for local fishing operations.
“It’s super important to monitor those species because it’s a really good indicator of the health of those ecosystems,” Pérez Puig said.
The three scientists disappear back behind their binoculars, as the boat bobs near the remote, cactus-studded San Pedro Mártir Island.
An orange jellyfish drifts by. Pérez Puig says these animals were once characteristic of warmer, more tropical waters — but are now becoming common in these cold, winter waters of the Gulf of California.
He says fishermen tell him that, 30 years ago, they would sometimes witness hundreds of sperm whales at a time here. When he started monitoring the area in 2009, he would see groups of up to fifty at a time.
“All of these conditions indicate something related with the environmental conditions and the marine ecosystem. So it’s important to continue monitoring those species,” Pérez Puig said.
Today, the patch of Gulf that surrounds us is uninterrupted. No soplos. Just choppy blue waters toward the horizon.
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