The only large Arctic shark
Perhaps the Arctic’s most mysterious species, Greenland sharks (Somniosus microcephalus) are ancient and massive shadows in the deep, cold waters of the Arctic and North Atlantic Oceans.
Weighing an average of 900 kilograms, this huge predator is one of just two sharks (the other is the black dogfish) found in the Arctic. The Greenland shark is also one of the world’s largest sharks – they can grow up to 7 metres long, the same size as the great white shark – and the largest Arctic fish.
It will eat and prey upon almost everything – in fact, practically every marine animal has been found in the stomach of a Greenland shark – including eels, whales, seals, sea urchins, crabs, fish, other sharks, and even the remains of land mammals that can be scavenged in the water, such as polar bear and caribou. (These larger species can present a challenge, as demonstrated by a shark that choked on a large slab of moose in November 2013).
Greenland sharks are slow-moving, to the point that they’re often called ‘sleeper sharks’. These bottom dwellers are often blinded by parasites that feed on their eyes but may help attract prey, acting like a colourful fishing lure.
Why Greenland sharks are important
The Greenland shark’s role as a top predator in the Arctic marine environment makes it an important species to know and understand.
With very little research available, there is a lot to learn about Greenland sharks. Current knowledge is based primarily on anecdotal information from local traditional knowledge, which experts at the University of Windsor – WWF partners in Greenland shark research – compiled through interviews with community members.
At this point, efforts are focused on establishing baseline knowledge, so change can be measured. As Greenland sharks are believed to be very long lived, they are likely slow to reproduce, meaning any activity that affects their numbers can have a severe and long-term impact on the population.
Better understanding these sharks – where they live and for how long, what they eat and when, where they mate and pup, how may pups they birth – and how they’re affected by human activity is critical to ensuring they have a healthy future ahead.
Threats to Greenland sharks
Fortunately for researchers, Greenland sharks are easy to catch. Unfortunately, this means that they are often accidently caught in fishing equipment (bycatch, as it’s known in the industry), particularly by Nunavut’s turbot fisheries. Because Greenland Sharks are not edible, they are discarded when caught.
The fact that these sharks have such varied and voracious appetites could also put them at risk, as increasing development in the Arctic can lead to them eating all kinds of waste that is not part of the Greenland shark’s natural diet. Their important habitat areas may also conflict with development, as researchers are beginning to observe and interesting interaction between shark and whale movement in the Arctic, likely connected with their pursuit of food.
As top predators in a complex food web, Greenland sharks will likely be affected by changes to their environment, such as climate change. They could also become vulnerable to attacks by predators new to Arctic waters, such as killer whales.
With so little information available, it’s hard to predict how these threats will impact Greenland shark populations, which are currently believed to be healthy.
What WWF is doing
Making sure Greenland shark populations stay healthy means knowing more about them. WWF is supporting and participating in research lead by the University of Windsor to tag and track Greenland sharks. This is part of the Ocean Tracking Network, a global monitoring network that "is providing the scientific foundation for sustainable oceans management," working with marine scientists around the world.
Among the first efforts to monitor these sharks, the project’s results will shine a light on the critical habitat where they hunt, mate and pup, as well as how many young they have and when they reach maturity. Currently, these are unanswered questions. Without this information, understanding the impact of fisheries and other human activities – and more importantly, finding ways to reduce or eliminate those impacts.
In the summer of 2013, WWF’s Vicki Sahanatien joined the University of Windsor team to tag Greenland sharks in the Canadian Arctic, in an effort to learn more about these mysterious creatures. Watch this slideshow of the team in action.
Greenland Shark Basics
Average length: 6.5 m (up to 7 m)
Average weight: 900 kg
On the Move
Greenland Shark Experts
Learn more about their Greenland shark tagging expeditions.