The cold, dark waters of the Skagerrak – a strait between Denmark, Norway and Sweden – have been identified as a crucial nursery area for young Greenland sharks, according to a new study.
The research, published in the journal Ecology and Evolution, sheds new light on the life of one of the ocean’s most mysterious creatures.
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Skagerrak: a nursery for Greenland sharks
The Greenland shark is famed for its centuries-long lifespan, enormous size (up to 6.4 metres from snout to tail tip) and slow-moving nature in the deep Arctic.
But the new study reveals something surprising: drawing on records of 1,610 individuals from across the North Atlantic, the Skagerrak recorded the highest proportion of young sharks (between 90 and 200 centimetres).
"We consider the deepest areas of the Skagerrak to be a potentially important feeding ground for ‘teenage Greenland sharks’,” explains associate professor and marine biologist Peter Rask Møller from the Natural History Museum of Denmark.
It’s believed the rich biodiversity and productivity of the Skagerrak makes the area an attractive spot for the Greenland sharks, which feed on a variety of prey, including fish and marine mammals. They also scavenge for carrion.
The occurrence of so many young Greenland sharks in the Skagerrak challenges long-held assumptions that the elusive animals are born in Arctic waters, say the researchers.
Where are Greenland sharks born?
The team’s extensive analysis – including reviews of museum specimens and unpublished databases – found that newborn sharks, typically 40 centimetres long, are likely to be born near the Mid-Atlantic Ridge, south of Iceland, rather than in the Arctic.
“Future targeted studies will most likely confirm that the Greenland shark gives birth to its many pups in undisturbed parts of the deep sea near the Mid-Atlantic Ridge in deep waters, where there is little activity from commercial fisheries,” says the study’s lead author Julius Nielsen.
While the sharks’ early lives may begin in the Atlantic depths, their adolescent years seem to be spent closer to mainland Europe. Historical records, including 150 years of strandings and bycatch data from Denmark, as well as recent catches from Swedish recreational fishers, support the idea of Skagerrak as an important juvenile habitat.
Why is the study important?
The Greenland shark is considered Vulnerable on the IUCN Red List of Threatened Species. The researchers say, “the findings on the whereabouts and life history of Greenland sharks allow for more precise conservation measures to be enforced.
“The longevity of Greenland sharks is exceptional, and we consider regional protection to be of great importance to counteract the present Red List status.
“This study provides new insights into the life history of the Greenland shark, which will aid the development of targeted conservation measures,” the authors conclude.
Top image: Greenland shark. Credit: Julius Nielsen
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