Scientists specialized in fishery resources and marine life in the United States have estimated that between 2018 and 2020, about 10 billion snow crabs (a species with the scientific name Chionoecetes opilio) died in the Bering Sea (North Pacific, between Alaska and Siberia). The loss was so great that it forced the cancellation of the 2022-23 fishing season for these crustaceans of notable commercial and gastronomic value.
The causes of this event, considered one of the largest episodes of massive marine mortality since studies of this type were carried out, were until now divided between various environmental and human factors.
A new scientific study, published (October 19) in the journal Science by experts from the Alaska Fisheries Science Center (United States), indicates that the first and main cause of the mass death of these crabs was the increase in water temperature recorded in this area near the Alaska coast in 2018. The increase of up to 3 degrees in water temperature triggered a tragic episode of food shortage, concludes the research team led by Michael Litzow.
To solve the mystery of the multi-million-dollar crab die-off, the study's authors have analyzed data from recent years on water temperatures and catches, as well as reviewing previous research on how snow crabs respond to warmer temperatures. .
Alaskan fishermen and scientists first noticed a dramatic decline in the amount of resources and catches of this crab species in 2021. Then, due to the Covid pandemic, fishing and studying crabs was suspended for several months .
The full magnitude of the disappearance of these crabs in the Bering area was not observed until early 2023: more than 10 billion specimens were missing. Upon discovering this alarming decline, a research team set to work to discover what had happened, explains the Alaska Fisheries Science Center in a release note on the study.
The team began exploring nearby areas, hoping that the crabs had simply moved to other areas, but they could find no signs of these missing populations.
As part of the study, the authors found that the affected area had experienced a heat wave before and during the disappearance of the crab, so they reviewed the results of a previous study that found that when water temperature increases, the needs of energy (food) for the crabs. The researchers found that if the water temperature increased just 3°C, the crabs' caloric needs doubled.
Records showed that during the heatwave, water temperatures had risen by just 3°C, meaning the crabs would have needed twice as much food to sustain themselves. The research team also found that just before the heat wave, the crab population had increased dramatically, meaning there had been a huge increase in competition for food. And that, the researchers conclude, led the crabs to starve.
Preliminary data on this investigation were released last June in a report by Alaska Public Media and KMXT.
