8 billion crabs disappeared from Alaskan sea in 3 years, what is the cause?
In Alaska, the United States, crab fishing has been banned from 2022 to 2023 due to the sudden disappearance of 1 billion crabs, which has decreased by 90% compared to before. Live Science, a scientific news site, is considering what caused the disappearance of crabs while experts are investigating the cause.
What made billions of snow crabs disappear from the Bering Sea? | Live Science
The Alaska Department of Fisheries and Game (ADF&G), which has jurisdiction over Alaska's fisheries, issued an advisory dated October 10, 2022, stating, 'Because the snow crab population is below the threshold, snow crab fishing will be prohibited in 2022-2023.' ” announced. This is the first time snow crab has been banned in Alaska, and the king crab fishing, which has been restricted for two consecutive years from 2021, has had a huge impact on the local industry. There is a sorrowful voice calling out.
An estimated 1 billion crabs disappeared and Alaska's crab fishing season was canceled - GIGAZINE
``It was the hardest decision I've ever made,'' Miranda Westphal, a regional management biologist at ADF&G, told Live Science.
According to a September 2021 report by The Seattle Times, about 3 billion adult snow crabs and 5 billion young fish lived in the Bering Sea in 2018. However, it is known that in the second half of 2021, the number of adult crabs will be 2.5 million and the number of juveniles will be 6.5 million, with nearly 8 billion crabs disappearing in just three years.
One of the reasons why crabs have disappeared is overfishing. In a February 2022 notice , the National Marine Fisheries Service warned that Bering Sea snow crab, along with groupers in the Gulf of Mexico and mackerel in the Atlantic, are being overfished.
In addition, it has been pointed out that there are problems not only in the amount of catches but also in fishing methods. There are other fisheries in the Bering Sea other than crab fishing, and trawlers that are not intended for crab are returning snow crab as bycatch to the sea. However, many crabs die as they are due to the impact of being suddenly raised to the sea surface and thrown back into the sea, and according to a survey conducted by ADF&G in 2020, ``30% of snow crabs thrown back into the sea are dead.'' It is guessed.
Meanwhile, The Seattle Times reported in an April 2022 article , ``Unsustainable fishing may be playing a role in crab decline, but the main culprit is arguably man-made climate change.'' .
Reportedly, the growth of snow crabs requires cold water that flows north of the Bering Sea, which is located in the northernmost part of the Pacific Ocean. It is an important element to do.
As seawater cools, it sinks to the seafloor, forming a layer of cold water that marine biologists call a 'cold pool.' This cold pool is a sanctuary for juvenile crabs because other fish and predators can hardly get close to it. I'm here.
However, according to the survey results reported by the National Oceanic and Atmospheric Administration on September 2, record heat waves that occurred in 2016, 2018, and 2019 inhibited the formation of cold pools in the Bering Sea, and juvenile crabs found to be less protected from predators. ADF&G's Westphal also points out that it's likely that the crabs went into starvation mode as the water temperature increased and the metabolism of adult crabs accelerated.
Human-made climate change is becoming more intense each year, and heat waves that destroy crab sanctuaries are expected to become more frequent. Jamie Goen, executive director of Alaska Bering Sea Crabbers, an industry group organized by crab fishers in Alaska, said in an interview with KIMA-TV, a television station in Washington state, ``People who go bankrupt and can no longer support their families, sell their homes. Some people will have to, some will give up their boats, and all the seasoned fishermen who have worked on those boats for many years will lose their jobs.'
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