Championing indicator species for deep-sea conservation
We know little about deep-sea sharks and rays, but threats to their conservation are on the rise and we risk losing them before we know them. The Greenland shark can live for centuries. The sailray is one of the least known species, found in the deep North Atlantic and Arctic oceans. Gustav is using these as indicator species for biodiversity hotspots in Skagerrak, where interest in deep-sea exploitation is rising and no marine protected areas safeguard deep-sea habitats and species. He uses deep-sea fish tracking to map their behaviour, home ranges, migrations and survival, gathering knowledge that will support management and conservation.
Gustav Hellström
Growing up amid the forests, marshes and mountains of central Sweden, I wasn’t initially drawn to the sea. As a child, armed with a fishing rod I would explore the creeks and lakes near my home, developing a profound fascination for fish. Peering into the waters, I often wondered about the lives of these creatures in the depths below. Unfortunately, an early fear of water – an unusual trait for a budding marine biologist – hindered me from exploring these wonders until later, during my PhD studies on fish behaviour and the introduction to fish-tracking technology. This technology...
Skagerrak's hidden gems - exploring deep sea elasmobranchs in one of the world's most exploited seas
The primary objective of this project is to conserve the deep-sea ecosystems of Skagerrak by focusing on Greenland sharks and sailrays as indicator species for biodiversity hotspots. We aim to achieve this by using deep-sea fish-tracking infrastructure to map their behaviour, home ranges, migrations and survival, and thus acquire the knowledge that will support future management and conservation efforts in light of increased deep-sea exploitation in the region.
Interest in deep-sea exploitation in the Skagerrak is growing, with plans to expand fisheries and offshore development. Deep-sea elasmobranchs, like the Greenland shark and the sailray, are currently overlooked in management strategies. Understanding the habitat, migration and survival of these species is essential to guide conservation and management, particularly for the little-known sailray. Identifying and mapping deep-sea biological hotspots is crucial for supporting the upcoming expansion of protected areas under the ‘30 by 30’ initiative.
Deep-sea elasmobranchs are among the least understood fish in our oceans. The Greenland shark, potentially the oldest vertebrate on the planet, can live for centuries, reaching maturity at about 100 years of age, which makes it vulnerable to exploitation. Although they were once considered rare in Skagerrak waters, specialist anglers have recently identified areas in northern Skagerrak where Greenland sharks are frequently caught, along with various other species, including sailrays. Our initial studies indicate that these sharks may be confined to relatively restricted deep-sea areas, constituting biodiversity hotspots within the otherwise heavily exploited Skagerrak waters.
The sailray, one of the least-known elasmobranch species, is found in deep waters of the North Atlantic and Arctic oceans, with Skagerrak at the southern edge of its range. It is the deep-sea elasmobranch most commonly taken as bycatch in Skagerrak’s demersal trawl fisheries, and several tonnes are captured annually. Due to a lack of information, no specific catch regulations or management plans exist for this population.
Countries around Skagerrak are currently planning new marine protected areas as part of the global ‘30 by 30’ initiative and evaluating regions based on habitat types, species diversity and connectivity to existing marine protected areas. Currently, no marine protected area protects large deep-sea habitats in Skagerrak and, as many deep-water areas are heavily trawled, there is resistance to the expansion of marine protected areas into these regions. Our study area is bordered by three large coastal marine protected areas, making it an excellent candidate for designation as a marine protected area due to its potential connectivity. Additional data on the Greenland shark and sailray are crucial to support the conservation value of this area and strengthen its case as a candidate to become a marine protected area.
The overall aims of the project are to conserve Skagerrak’s deep-sea ecosystems, focusing on Greenland sharks and sailrays as biodiversity indicators, and to increase our understanding of their behaviour and movements to support effective management and conservation strategies amid increasing deep-sea exploitation. This will be achieved by:
- Mapping and monitoring: using deep-sea tracking infrastructure to study the behaviour, migrations, home ranges and habitat use of Greenland sharks and sailrays.
- Conservation planning: utilising research to develop targeted conservation strategies and influence policy in the study area, with the expansion of the marine protected area as a priority.
- Public engagement: raising awareness about Skagerrak’s deep-sea ecosystems through media and stakeholder engagement.