A Storm of Snow Crabs?

This map shows the snow crab population in the Barents Sea, steadily moving westward from the Russian to the Norwegian zone and heading toward Svalbard. (Image: Courtesy of PINRO)

The blizzard of snow crabs in the Barents Sea is heading toward the fragile ecosystems of Svalbard, and there may not be time to react.


Scientists recently learned that the total biomass of snow crabs is ten times higher than king crabs in the Barents Sea.  What’s more, the snow crabs have reached these high numbers in a far shorter period of time:  the king crab was intentionally released into the Barents Sea in the 1960s, but its presence was not detected in high numbers until the early 90s.  By contrast, the snow crab has spread throughout the Russian area of the Barents Sea in less than 20 years, with the exception of the southern areas inhabited by the king crab. And unlike the king crab, the snow crab seems to be making its way across the sea without the aid of humans.

Now scientists are watching the seemingly relentless spread of the snow crab westward into Norwegian waters, and the unique Svalbard archipelago is in their path.  Although the densest part of the snow crab mass is still several hundred kilometers to the southeast, there has already been at least one snow crab sighting in the eastern Svalbard region. 

The storm may be too close to prepare for.  Nevertheless, the office of the Governor of Svalbard has decided to delay the official release of its invasive species action plan in order to incorporate a thorough analysis of the snow crab situation.

“It could be a disaster,” said Espen Stokke, senior adviser for nature management at the office of the Governor of Svalbard.  “I’m not sure if it is possible to make a strategy to keep the snow crab out.”

Nearly 90 percent of the shallow waters surrounding Svalbard are a conservation area, and eastern Svalbard is one of the newest additions.  As with marine communities in general, the health of the Svalbard marine ecosystem is largely dependent on robust primary productivity, which refers to the photosynthesis of new organic material by phytoplankton in the upper layers of the ocean.  Primary production toward the top is in turn related to the health of what is called the benthos at the bottom – the community of organisms on the sea floor, consisting of animals like mussels and polychaetes that help to recycle nutrients back into the upper layers of the ecosystem.

But scientists fear that the approaching mass of snow crabs may make short work of Svalbard’s important benthic community.   

Jan Sundet, senior scientist at the Institute for Marine Research in Tromsø, said that the further north you go, the more important the benthic community is for secondary production.  This means that in the Arctic, a greater portion of the molecules photosynthesized by primary producers – molecules like organic acids, proteins or long carbohydrate molecules called polysaccharides – will sink to the bottom as sediment, as compared with areas further south.

Snow crabs, like king crabs, are notorious for eating just about everything in sight in the benthic zone.  This includes decaying matter, organisms that aid in decomposition and organisms that help oxygenate the sea floor – all part of the vital nutrient cycling processes in the benthos. 

Sundet said that the snow crab invasion is a top priority for IMR and for the Norwegian authorities, to whom he recently provided requested scientific advice regarding the snow crab situation.  From a scientific perspective, he said a major concern is the lack of baseline information about the threatened eastern side of Svalbard.  This will be crucial in developing a strategy for when – not if – the snow crab arrive. 

“Ecosystems in this high Arctic area are very vulnerable to introduced species like the snow crab,” Sundet said.  “Although the snow crab might have entered the Barents Sea as a result of widening its home range, the consequences of its appearance will be as if it is an alien species. Action must be taken from that standpoint.”

The Ministry of Fisheries does not yet have an official stance on the snow crab situation.