Fedewa noticed that something wasn't right when he counted snow crabs at sea.
Fedewa is part of a team that collects crabs from 376 stations in Alaska's Bering Sea each year. The areas teem with crabs all the time. Thousands of scientists are counted. The number of people dwindled to hundreds.
She said that the survey last year was a red flag.
The people who predicted it were correct. The population of snow crabs plummeted after hitting a record high. The snow crab fishing season was canceled for the first time due to low numbers. The total snow crab population in the eastern Bering Sea dropped from an estimated 11.7 billion in the year of the survey to 1.9 billion in the year after. It was a drop of over 80 percent.
Billions of the creatures are thought to have been wiped out.
Fedewa said that all they could point to was a large-scale mortality event.
It's an episode that is believed to have been caused by the warm ocean waters in the northern part of the world. It's possible that it's a consequence of climate change, which can make the environment more extreme.
A NOAA graph showing the major decline in total Bering Sea snow crab abundance, in billions, as estimated from the agency's annual bottom trawl survey. 2020 is a missing data point because the survey was canceled due to the global pandemic. Credit: NOAA / Alaska Fisheries Science Center
Crabs have historically flourished in the sea.
Matthew Bracken, a professor of ecology and evolutionary biology at the University of California, Irvine, said that the Bering Sea is changing rapidly.
There was a marine heat wave in the northeast Pacific Ocean in 2019. Climate change has been blamed for the recent heat wave. The Bering Sea experienced unprecedented warming over the course of the last two years. Similar to more frequent heat waves on land, marine heat waves are growing more frequent and intense. Higher temperatures boost the chances of a marine heat wave occurring. Warming of the planet is likely to be the reason. Researchers concluded in a recent study that the multi-year persistent marine heatwave was caused by temperature forcing by elevated greenhouse gases levels.
How this heat caused a huge die-off of crabs is a big question. The crucial point is that warmer temperatures can amplify the mechanisms of death. The graph above shows that snow crab numbers can change quickly. There was a dramatic fall in the species in 1999.
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What could have happened in warmer water?
Warming ocean waters are a major factor in the decline of sea ice. At a time when the water should have been covered in ice, the Bering Sea ice almost completely vanished in March of 2019. The ice extent was the lowest in satellite history. Losing ice is bad news for snow crabs. The cold pool created by the melting of sea ice is too cold for fish to swim in. The refuge is for baby crabs. There may have been no place for baby crabs in 2019.
The warmer waters allow diseases to thrive. The snow crab population is susceptible to disease. Warming water temperature gives a place for disease to come into the system. There are more pathogens that can live.
"The Bering Sea is changing dramatically right now."
It is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556 is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556 The issue noted by Fedewa is an important one. Commercial fishermen target mature crabs, the type they can sell. Fedewa believes the population decline was caused by a bottom-up driver, meaning something widespread impacted crab numbers at lower levels in the food chain.
It's1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556 That is currently not likely. The survey didn't account for the vanished crabs. There is no clear answer as to where they could have crawled.
Snow crabs photographed by NOAA. Credit: NOAA Fisheries
Fedewa noted that new, younger crab were found in their survey gear. The crabs are five or so years away from leaving their grounds, but this could mean that some of the population could bounce back.
The collapse was driven by what the scientists at the National Oceanographic and Atmospheric Administration are studying. The mass of male snow crabs that can be legally harvest fell by 44 percent. It's under one third of the 20-year average. It's a huge loss of flora and fauna. A couple years ago, the Alaskan industry produced $132 million in revenue.
"Science points to temperature and bigger picture climate change."
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There is evidence that supports the changes taking place in the north. The impact of a warming ocean on snow crabs is not surprising.
Fedewa said that science points to temperature and climate change.
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