A recent study conducted by the National Oceanic and Atmospheric Administration (NOAA) points to the detrimental impact of rising ocean temperatures on the snow crab population in Alaska’s Bering Sea. The unexpected loss of billions of snow crabs has not only prompted concerns about ecological balance but has also led to the postponement of the snow crab harvest season for the second consecutive year.
Authored by Cody Szuwalski, a fishery biologist at NOAA, the study establishes a compelling connection between marine heat waves in the eastern Bering Sea and the mysterious disappearance of snow crabs. Szuwalski expressed initial astonishment when analyzing the 2021 survey data, stating, “My mind was just blown.” However, subsequent research revealed that this was not a transient issue but a long-term ecological concern.
While overfishing has been a longstanding concern for declining snow crab populations, experts emphasize that the term “overfished” is a technical definition triggering conservation measures, leaving the actual cause of the collapse unexplained. Szuwalski points to climate change as a new challenge, disrupting established management systems and scientific predictions.
The research explored two primary possibilities: migration or mortality. Extensive investigations in various regions, including the northern Bering Sea, Russian waters, and deeper ocean levels, led scientists to conclude that migration was improbable. Instead, warmer temperatures and higher population density emerged as significant factors linked to increased mortality among mature snow crabs.
Cold-water species like snow crabs typically inhabit areas where water temperatures remain below 2 degrees Celsius. However, they can tolerate waters up to 12 degrees Celsius. Warmer ocean temperatures disrupted their metabolism and escalated their caloric requirements. The two-year marine heat wave of 2018-2019 led to a fourfold increase in the energy snow crabs needed from food. Unfortunately, the heat wave severely disrupted the Bering Sea’s food chain, making it challenging for snow crabs to forage and meet their caloric needs.
Adding to the complexity, other species like Pacific cod seized the opportunity presented by the temporary disappearance of the temperature barrier that usually separates them from the snow crab habitat during the heat wave. This intensified competition for limited resources, exacerbating the crabs’ predicament.
As a stark reminder of the rapidly intensifying climate crisis, the vanishing snow crabs highlight the multifaceted impacts on marine ecosystems. Szuwalski acknowledged the inevitability of such changes but expressed surprise at their swift unfolding. A long-term consequence is anticipated, with the snow crab population expected to shift north as ice continues to recede, diminishing their presence in the eastern Bering Sea.
