A new study on the mysterious Greenland shark (Somniosus microcephalus) suggests that the animals are born in the deep mid-Atlantic and increasingly move toward Europe as they enter their “teenage years.” Researchers identified the Skagerrak Strait between Denmark, Norway and Sweden as their preferred habitat and hunting ground during this stage.
Giants of the cold – and of time
Greenland sharks can reach lengths of up to 6.4 meters and live for several centuries. They prefer cold, often deep areas of the North Atlantic and are frequently caught as bycatch in fishing gear – a risk for this still little-studied species. For the new study, 1,610 individuals from 11 regions were recorded by size, sex, and developmental stage.
In most regions, subadult females dominated. Adult females were rare or absent in the Canadian Arctic (north) and around Svalbard, but were significantly more common in southwest Greenland and Iceland. In the southern Canadian Arctic as well as off northwest and southeast Greenland, adult females were mostly found in offshore areas – at depths of 25 to 1,375 meters and water temperatures between −1.54 °C and 10.9 °C. Adult females preferred temperatures above 4 °C.
Off she goes! We have now tagged our first Greenland shark in the Skagerrak sea. A 3.5m beauty! 😍These calm giants are mesmerizing, and I can't wait until we get the data back. Epic teamwork by @HellstromKGV @DrBrodin, D. Palm and our skilled collaborators. @SLUwildresearch pic.twitter.com/R9S5V4ZtQ4
— Petter Lundberg (@lundberg_petter) July 20, 2022
Skagerrak as a youth meeting place – and a trail to the nursery
Larger juveniles were observed in many regions, but were particularly common in the Skagerrak and in offshore areas of the southern Canadian Arctic. Newborns or very small juveniles remained rare – but data from scientific archives and collections revealed a striking cluster along the Mid-Atlantic Ridge and in the Irminger Sea. This suggests that the main birthing grounds are more likely located there rather than – as previously assumed – around Baffin Island in the Canadian Arctic.
One advantage: these deep mid-Atlantic areas are less affected by fishing, which could benefit the offspring.
Need for protection of large females
The Greenland shark is listed as “vulnerable” on the IUCN Red List. Against this background, researchers recommend targeted protection measures for large and potentially reproductive females: both in coastal and offshore waters of southwest Greenland, in the offshore areas of the southern Canadian Arctic, in southeast Greenland, and in Iceland.
The results provide a geographical roadmap for protection: nurseries in the deep mid-Atlantic, juvenile habitats in the Skagerrak – and priority for adult females in selected regions.
The study was published in the journal Ecology & Evolution.
