Why they are dieing ?

Tourists come here from around theworld to watch whales. It’s common to see humpbacks leaping out of the waterand fin whales slapping the waves with their flukes. If you’re lucky, you’ll catch a gray whale poking its head out of the water to scope out the surroundings. And if you’re really lucky, you’ll see a blue whale — at up to 165 tons, the largest animal on earth.

But all is not well here this year. Gray whales are dying in large numbers. Since January, at least 167 North Pacific gray whales have washed ashore dead from Mexico to Alaska. That’s probably just a fraction of the number that have actually died. Most will have sunk to the sea floor; scientists call these carcasses “whale falls.” But the number of known deaths is high enough that the National Oceanic and Atmospheric Administration has declared an “unusual mortality event” — a pronouncement that has sent scientists scrambling to figure out what’s going on.

Events like this are often the first warning sign that something may be seriously amiss below the waves. Particularly striking is that many of the whales washed ashore have been emaciated.

Despite the toll humans have exacted on them, gray whales, which can reach 49 feet in length and weigh 45 tons, are known for their curiosity about boats and friendliness toward people. Each spring, they migrate roughly 5,000 miles from their birthing grounds in the warm, shallow lagoons of Baja California in Mexico to their feeding grounds in the frigid waters of the Bering Sea off the Alaska coast, where they feast daily on up to 1.3 tons of mostly small crustaceans called amphipods. It’s crucial for these whales to eat enough to survive the grueling 10,000-mile round-trip migration, among the longest of any mammal.

When these whales returned to their Baja breeding grounds in early spring this year, they arrived weeks late and were skinnier than usual. Now, not only do some of the adults seem to be malnourished as they pass by on their return trip to the Arctic, but we are also seeing about one-third fewer calves than we did in last year’s count. Baby whales need 50 gallons of milk a day, with a fat content of 50 percent, which means their mothers need to be well fed.

This isn’t the first time a big die-off has occurred in the Northeast Pacific. Twenty years ago, NOAA issued an “unusual mortality event” notice when over 100 gray whales washed up on West Coast beaches. Scientists were never able to identify the cause.

Isolating the cause of this year’s mysterious deaths is a tremendous challenge. Interdisciplinary teams of scientists have begun sifting through a profusion of data — for example, sea ice extent, ocean temperature, food availability, entanglement in fishing gear, marine pollution, toxic algae blooms, collisions with large ships and predation by killer whales. In a sense, this is old-fashioned detective work, but the world they are working in is mostly hidden and inaccessible, where everything is moving all the time.

Perhaps the gray whale population — now estimated to be about 27,000, a quarter of what it was when commercial whaling peaked in the mid-1800s — simply exceeded the ocean’s capacity to support them this year.

We also know that climate change is touching every part of the ocean, including here in Monterey Bay. Temperatures are warmer, there is less oxygen in the water and the sea has become more acidic. A study using multiple climate and ecosystem models, published this month, projected that for every 1.8 degree increase in ocean temperature, there is an associated 5 percent drop in the total mass of sea animals.

Last summer, the whales’ prime feeding habitat in the Bering Sea was more than eight degrees warmer than average. Scientists are working to understand whether this anomaly affected the amphipods that are the main source of food for the whales. Researchers think the amphipods eat algae that grow on and within the sea ice. But with sea ice melting, there is less algae and fewer amphipods. The maximum sea ice extent in 2018 was the lowest it has been in the last 41 years.

In the coming months, scientists will gain a clearer picture of what’s been happening. In the meantime, we can help these animals by supporting the creation of more protected areas in the ocean, like the Monterey Bay National Marine Sanctuary. These places are strongholds of biodiversity that provide resilience against threats like climate change. NOAA is also working with the private sector to modify shipping routes and adjust fishing techniques. The health of these gray whales depends on the health of the ocean. So does ours. We must do everything we can to better understand and protect that world.