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The Guardian

Why do dead whales continue to wash dishes in San Francisco?

A recent wave of deaths in the region has raised concerns, but scientists say it may not be a sign of disaster. Photograph: The Marine Mammal Center / Reuters The 45-foot hulk lay face down in the waves at Fort Funston Beach, just south of San Francisco, drawing a small crowd of hikers and hang-gliders. The stench lingered in the evening breeze as seabirds surrounded the animal, a juvenile fin whale. The whale was the fifth to run aground in the region this month. The other four were gray whales – giant cetaceans that migrate an incredible 11,000 miles each year from Alaska to Baja and vice versa – all found on beaches near town over a period of just eight days. Each was a startling scene that raised immediate concerns for many observers. Whales are an important part of the ecosystem, often seen as markers of ocean health, and their deaths can serve as an indicator that something is wrong. But scientists say the picture is more complicated. Investigations into whale deaths continue and so far, experts say, there is no smoking gun. Some marine researchers believe deaths may be more cyclical than a sign of disaster. “At first glance, it looks horrible,” says Joshua Stewart, associate researcher with the National Oceanic and Atmospheric Administration (Noaa). “But this is not an isolated event and to some extent it makes me feel personally at ease.” After nearly extinction in the 1950s, gray whales have experienced a remarkable recovery, rebounding to levels that allowed their removal from the endangered species list in 1994. Now, they are among the most commonly seen along from the California coast as they migrate south for the winter and north in early spring. They are also one of the most studied marine mammals, with data dating back to the 1960s. Each time a whale ends up ashore, it gives scientists a new opportunity to learn more about the state of the sea. seas. However, the gray whale population on the west coast has declined in recent years – down about 24% since 2016. Today, there are around 20,580 whales left, according to data from Noaa. And this month’s strong wave of deaths was not the first – in 2019, Noaa declared an ongoing “unusual mortality event” when 122 whales stranded on the west coast from California to Alaska. , more than four times the 29 Stewart’s last 18-year average, which tracks gray whale population numbers, notes that, even with the declines, the population is still near an all-time high. “Despite these slowdowns which at the time were very painful, they rebounded a number of times,” he says, adding that it is a highly adaptable and resilient species. “We want to know if this decline is continuing or if it is temporary.” Gray whales are among the most studied marine mammals. Photograph: Guillermo Arias / AFP / Getty Images On April 8, there were two whales to be examined in the bay at the same time. A carcass had been floating for days before finding itself housed at the Berkeley Marina. The other ran aground on Muir Beach, just north of San Francisco. Teams from the Marine Mammal Center and the California Academy of Sciences performed autopsies, which include taking tissue samples, evaluating internal organs and the reproductive system, and evaluating ribs and vertebrae for detect signs of trauma or impact. Moe Flannery, senior director of bird and mammal collections for the California Academy of Sciences, was at the scene for the autopsies and said the teams had not completed their investigations – although the culprits may include a lack of food or disease. “There are no real answers yet,” she said, adding that despite the deaths, scientists are hoping the gray whale population will rebound. “It is a resilient species and I think it is worrying, but we have the hope that it is only a small leap in time and that the species itself will bounce back as it did.” in the past. Collisions with ships have already been identified as the cause of some deaths, including the fin whale found on Friday. Unlike gray whales, fin whales are still considered endangered. Only about 3,200 remain along the west coast off California, Oregon and Washington, and ship strikes are the greatest threat to their survival. “It shows how many threats these whales face,” says Callie Steffen, project scientist at the Benioff Ocean Initiative. Steffen works in a team that developed Project Whale Safe, which uses data to help sailors map where whales are found when planning trips off southern California. The system, which she says is “like a warning from the late Smokey the Bear but to the whales”, has had a positive impact. But whales can move closer to shore, putting them at a higher risk of damage from ship strikes, loud disruptive noises from ports, chemical pollution and entanglement, according to a study by 2019 from the Scripps Institution of Oceanography at the University of California at San Diego. . The study’s authors believe the change has something to do with the whale’s biological clocks. Ari Friedlaender, a marine ecologist who teaches and runs a laboratory at the University of California at Santa Cruz, says that whether whales are killed by malnutrition or by collisions with ships, their deaths should be taken as a signal of ‘alarm. While we can’t point a finger at a singular cause behind the decline, human activity – from shipping to the climate crisis – is driving changes that are negatively affecting whales. “This means that people are affecting and possibly altering the ecosystems that these whales need for food,” says Friedlaender. “There are so many downstream effects and impacts of what we do in our daily lives. The actions we take locally can have consequences and impacts very far away and over longer periods of time. We must keep our eyes open. “

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