Wildlife

Snow Crabs Disappear

The Bering Sea's snow crab population has been in decline over the last five years, but this season the population has collapsed.

Snow crabs in the Bering Sea once numbered in the billions. But after a recent and massive population crash the crabs have all but vanished from these waters — and they may not be coming back anytime soon.

In 2018, about 3 billion mature snow crabs (Chionoecetes opilio) inhabited the Bering Sea along with roughly five billion immature crabs, the Seattle Times reported(opens in new tab). But by late 2021, those numbers hovered around 2.5 million and 6.5 million, respectively — a loss of nearly eight billion crabs in just three years. In Februarythe Alaska Department of Fish and Game (ADFG) made the difficult decision to cancel the season's snow crab harvest for fear of wiping out the crustaceans altogether.

What caused the snow crab crash? The main culprit was almost certainly human-caused climate change, though unsustainable fishing practices may also have played a role.

Snow crabs thrive in the cold northern waters of the Bering Sea floor. For these crabs, water temperature isn’t just a matter of comfort; it plays a critical role in their lifecycle. As seawater cools, it becomes less salty and less buoyant, causing it to sink to the bottom of the ocean known as the "cold pool. Many fish and other types of marine life avoid the cold pool, but for juvenile snow crabs, it’s a sanctuary. With virtually no predators willing to venture into this layer's frigid waters, young crabs can grow up in peace.

But lately that protection has waned. Record heat waves in 2016, 2018 and 2019 stunted cold pool formation in the Bering Sea, leaving baby crabs vulnerable to predators. What's more, the warmer waters likely sped up the adult crabs' metabolism, causing them to starve.