The Alarming Decline of Alaskan Snow Crab Population

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The Alaskan snow crab population is declining drastically and scientists are attributing the reasons to climate change. Water temperatures in the Bering Sea have been recorded as warmer than average in recent years, leading to low sea-ice cover. Since snow crabs are found in areas that have ice cover, the accelerated melting of sea ice is leaving them exposed to the threat of predators. In addition to climate change, commercial fishing industries are also believed to have contributed to the decline in population of snow crabs.

 

Chionoecetes opilio and Chionoecetes bairdi are among the ten types of crab species found in the cold waters of the North Pacific, particularly in the Bering, Beaufort and Chukchi Seas, Aleutian Islands and the Gulf of Alaska. Both of these species are commonly referred to as ‘Snow Crabs’. These crabs are highly valued for their sweet, delicate meat, and are a popular seafood delicacy enjoyed by people all over the world. Alaskan snow crabs are typically harvested during the winter months when they migrate to shallower waters to mate and feed, and are considered a sustainable and well-managed fishery by the Alaskan seafood industry.


 

      Image Source: WorldAtlas.com


These snow crabs are benthic animals and live on the soft and sandy Bering Sea floor at a depth ranging from 13 to 2,187 m, with an average depth of 110 m; they also burrow if threatened by predators like seals, octopi, fishes etc. They generally live at temperatures ranging from -1 to 5°C but can thrive in temperatures as high as 10°C (Animal Diversity Web). The formation of sea ice in the Bering Sea is essential to create a cold band of water on the ocean floor that allows the young crabs to grow. This plays a critical role in their lifecycle (NOAA Fisheries) which is estimated to be 20 years.

Decline in the Population of Snow Crabs

In an unprecedented event, the Alaska Department of Fish and Game (ADF&G) cancelled the snow crab season in October 2022 based on the 2022 National Marine Fisheries Service (NMFS) Trawl Survey results for Bering Sea snow crab. The reason cited for this decision was the decline in the population of snow crabs below the regulatory threshold to open up harvesting (New York Times, 2022). The decision came as a devastating blow to local fisheries where the seafood industry is an economic cornerstone (Anchorage Daily News, Jan 2022). According to the National Oceanic and Atmospheric Administration (NOAA) Fisheries data, the commercial landings of Alaskan snow crabs alone came to USD 219 million in 2021. Given the dire condition of the snow crab population, the decision appeared inevitable and consequently, the ADF&G in an advisory statement implored the stakeholders to manage the Bering Sea snow crab population focusing on conservation and rebuilding in order to allow the immature snow crab population to grow and proliferate in the Bering Sea.

The 2018 NOAA annual Trawl Survey revealed that the young snow crab population was booming; thereby, heralding a lot of hope for commercial fishing. On contrary to that, the 2019 survey presented a steep decline in the number of juvenile crabs. In 2021, the survey revealed that crabs of all ages, not just juveniles, had decreased sharply and the declining trend continued in 2022, resulting in cancellation of Alaska snow crab harvest.

 

Image Source: The Seattle Times

Factors Leading to Declining Population

The number of snow crabs went from 11.7 billion in 2018 to 1 billion in 2021 and the leading reason behind the disappearance is climate change (The Guardian, 2022). According to Dr. Mike Litzow, water temperatures in the Bering Sea were warmer than average in 2018 and 2019, leading to low sea-ice cover (CNN, 2022). Since snow crab is an Arctic animal, they are found in areas that have winter ice cover, which provides young crabs safe sanctuary from predators. However, in recent years this protection has waned due to the accelerated melting of sea ice, leaving them exposed to threat of predators like Pacific Cod. Furthermore, if the bottom temperatures go beyond 2°C, it will allow predatory species like the Pacific Cod, which prey on crabs, to come into the area. Warming waters and accelerated melting have therefore shrunk the habitat of the species (The Guardian, 2022). Another hypothesis is that crabs in a small habitat have led to increased metabolic demand, outstripping available food and leading to starvation (Arctic Business Journal, 2023).

The NOAA researchers are also looking into possible incidences of diseases caused due to concomitant increase in temperatures in the Bering Sea that might have led to population decline. In all plausible causes, there is a link between the warming ocean and the mortality event (The Guardian, 2022).

In addition to climate change, commercial fishing industries have also contributed to the decline in population of snow crabs (Los Angeles Times, 2022). Massive trawling nets and equipment targeting marine species in the Bering Sea inadvertently catch and discard snow crabs as bycatch. Even with snow crab harvest, often fishers throw out crabs that are deemed less than perfect. In most cases, the crabs are unable to survive the shock of being hauled to the surface and subsequently thrown back into water (The Guardian, 2022).

Dr. Mike Litzow, the shellfish assessment programme manager at the Alaska Fisheries Science Center for the NOAA, studied the possibility of snow crabs moving deeper towards northern Bering Sea, however after conducting a survey in the area it was seen that there was not enough space for crabs to move north. Furthermore, the hypothesis that stock moved to Russian waters could not be tested due to unavailability of data from the Russian side (SLATE, 2022).

Effect on the Economy and Community

Snow crab harvest is a big business in Alaska and therefore, the cancellation of crab season has far-reaching implications for industry, economy and the local community. The Bering Sea crab harvest grossed USD 280 million in 2016 (Anchorage Daily News, 2022). The decision to close the snow crab season will cost USD 3 million in tax revenue, spelling a financial disaster for Alaska (The Economic Times, 2022).

Snow crab harvest is a mainstay for as many as 65 communities that make up the Western Alaska Community Development Quota Programme. Each year these communities are allocated a portion of the annual fish harvest of some commercial species directly to coalitions of villages comprising Indigenous communities in order to provide social and economic opportunities for its residents (The Washington Post, 2022). Without any financial support to small businesses and crab fishers, significant repercussions will be felt in Alaska’s village economies.

Bottomline

Moving forward, new fishing policies are required to ensure the protection of marine species and sustainable forms of subsistence fishing. Stock building assessment, compensation for loss and monitoring of the Bering Sea ecosystem remains imperative to tackle the environmental crisis engulfing the world.

References

 Anchorage Daily News (2022). Alaska cancels Bering Sea king and snow crab seasons over worries of population collapse. https://www.adn.com/business-economy/2022/10/11/alaskas-bering-sea-king-and-snow-crab-seasons-canceled-over-population-collapse/

Animal Diversity Web. Chionoecetes opilio snow crab https://animaldiversity.org/accounts/Chionoecetes_opilio/ 

Arctic Business Journal (2023). Blame ‘Borealisation’ for the disaster befalling the snow crab. https://www.arctictoday.com/arctic_business/bering-sea-crab-crisis-a-sign-of-borealisation-and-big-changes-in-the-future-scientists-warn/

CNN (2022). Billions of snow crabs have disappeared from the waters around Alaska. Scientists say overfishing is not the cause. https://edition.cnn.com/2022/10/16/us/alaska-snow-crab-harvest-canceled-climate/index.html

Los Angeles Times (2022). Climate change likely culprit in Alaska snow crab collapse. https://www.latimes.com/business/story/2022-10-17/climate-change-snow-crab-collapse

Slate (2022). Why Did 11 billion Alaskan Snow Crabs Suddenly Disappear? https://slate.com/technology/2022/10/alaskan-snow-crabs-dead.html

State Climate Summaries (2022) https://statesummaries.ncics.org/chapter/ak/

The Economic Times (2022). Snow crab season cancellation costs half of Alaska’s yearly budget. https://economictimes.indiatimes.com/news/international/us/snow-crab-season-cancellation-costs-half-of-alaskas-yearly-budget/articleshow/94867757.cms?from=mdr

The Guardian (2022). Billions gone: what’s behind the disappearance of Alaska snow crabs?https://www.theguardian.com/environment/2022/oct/20/billions-gone-whats-behind-the-disappearance-of-alaska-snow-crabs

The Seattle Times (2022). Valuable crab populations are in a ‘very scary’ decline in warming Bering Sea.https://www.seattletimes.com/seattle-news/valuable-crab-populations-crash-in-a-warming-bering-sea/

The Washington Post (2022). Alaska’s snow crabs have disappeared. Where they went is a mystery. https://www.washingtonpost.com/business/2022/08/21/alaska-crab-climate/


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