A new study on the mysterious Greenland shark (Somniosus microcephalus) suggests that the animals are born in the deep mid-Atlantic and move towards Europe as they enter their “teenage years”. Researchers identified the Skagerrak strait between Denmark, Norway, and Sweden as a preferred habitat and hunting ground during this phase.
Giants of the cold – and of time
Greenland sharks can grow up to 6.4 metres long and live for several centuries. They prefer cold, often deep areas of the North Atlantic and frequently end up as bycatch in fishing gear, posing a risk to this already little-studied species. For the new study, 1,610 individuals from 11 regions were recorded based on 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 predominantly found in offshore areas, at depths of 25 to 1,375 metres 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 spot – and a trail to the nursery
Larger juveniles were observed in many regions but were particularly concentrated in the Skagerrak and offshore areas of the southern Canadian Arctic. Newborns or very small juveniles were rare – however, data from scientific archives and collections revealed a notable cluster along the Mid-Atlantic Ridge and in the Irminger Sea. This suggests that the main birthing areas are 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, the researchers recommend targeted conservation 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 around Iceland.
The findings provide a geographical roadmap for conservation: 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.