Between 2018 and 2021, the snow crab population along the Alaska coast declined dramatically, losing an estimated 10 billion individuals. The shortage was felt by the local fishing population, whose income depends on these animals. The unprecedented extinction of species has led Alaska to suspend snow crab hunting in the eastern Bering Sea for the past two years.
Scientists have been studying the phenomenon since its discovery and now suggest that the crabs likely starved to death as a result of intense ocean heat waves in 2018 and 2019, according to a study published in the journal Science. Other factors also contributed to the animals’ hunger, including an exceptionally large population that increased competition for food in 2018.
“It is a fishing disaster in the truest sense of the word,” study coauthor Cody Szuwalski, a biologist at the National Oceanic and Atmospheric Administration (NOAA), told ScienceNews.
Snow crabs are accustomed to the cold waters of the Bering Sea, whose temperature is typically less than 3°C below the surface. Although they can survive in warmer conditions, as the water temperature increases they must increase the amount of calories they consume.
Because of this, crabs had to find more food to survive during the Bering Sea heat waves of 2018 and 2019. At the same time, they also faced increasing competition for food due to a population explosion in 2018. There was not enough food to meet the needs of this larger and hungrier population, and many of them died of starvation, scientists say.
This theory is further supported by the fact that crabs caught after the heatwave began had smaller bodies than those caught in previous years. “From 2017 to 2018, calorie needs quadrupled,” Szuwalski said, noting that populations of salmon, seabirds and seals also declined during that period.
“We are seeing an increasing number of serious incidents related to extreme temperatures,” said Christopher Harley, a zoologist at the University of British Columbia who was not involved in the new research. “The list of severely affected species and ecosystems continues to grow.”
Meanwhile, some creatures have experienced population increases due to warmer water temperatures, including charcoalfish, suggesting that some species may be adapting more quickly to major environmental changes than others.
However, if ocean temperatures continue to rise due to humancaused climate change, the overall composition of species living in the Bering Sea will likely be very different from today, likely leading to biological imbalances, the researchers point out.