Escape hatch could spare undersized Arctic crabs
Researchers working in Norway’s Barents Sea say a simple modification to snow crab pots could sharply reduce the number of undersized animals accidentally caught in the Arctic fishery.
Research by Heriot-Watt and UiT The Arctic University of Norway found that adding circular escape gaps to traditional crab pots allowed smaller crabs to escape before the gear was retrieved, without affecting the number of legally sized, commercially valuable crabs brought onboard.
Snow crab is harvested across the northern hemisphere, including in Canada, Greenland, the United States, Russia and, since 2012, in northern Norway.
Anything we can do to reduce sorting on deck is a win both for fishers and for the crabs.
The species is not targeted by UK vessels, but scientists say the same principles could be applied to crabbing gear used elsewhere, including in the UK, if adapted for local species.
Reducing waste and improving animal welfare
Most snow crab in the Barents Sea is caught in conical metal pots covered in diamond-mesh netting.
In theory, smaller crabs should be able to crawl back out through the mesh once the smell of bait fades.
In practice, undersized crabs end up being hauled to the surface along with legal-sized animals.
Once caught, undersized crabs are sorted on deck and released back to sea. But the process exposes them to rapid pressure changes, freezing air temperatures and handling injuries, conditions that previous studies in North America have shown can lead to high mortality.
Dr Kristine Cerbule, from Heriot-Watt’s International Centre for Island Technology in Orkney, said: “Anything we can do to reduce sorting on deck is a win both for fishers and for the crabs.
“Improving size selectivity helps avoid unnecessary harm in this cold-water fishery.”
A simple alteration with a big impact
The team tested pots fitted with three rigid, circular escape gaps measuring 9.5cm in diameter.
Research vessel trials in December 2024, followed by tests onboard a commercial fishing boat early this year, found that the modified pots consistently allowed more small crabs to escape than standard designs.
Importantly for fishers, the escape gaps did not reduce the catch of legal-sized crabs. Laboratory checks during the research cruise confirmed that none of the larger crabs retrieved from modified pots were physically able to pass through the circular openings, demonstrating that the design avoids losing valuable catch.
The modification is inexpensive and can be retrofitted to existing gear, the researchers say.
Potential for wider use
Although crab fisheries vary between countries, the basic mechanics of baited pots are similar worldwide. Escape openings are already used in some crustacean fisheries, but they are not universal.
The scientists behind the new study believe the approach could be adapted for other crab species and other regions, including UK waters, provided the openings are redesigned to match local species and minimum landing sizes.
Cerbule said: “If you get the design wrong, you risk letting valuable catch escape.
“But with careful testing, simple additions like these can make fisheries more sustainable.”
“The UK’s brown crab fishery, which uses creels, could potentially benefit from this.”
Next steps
The team plans to return to northern Norway in January 2026 to continue the research, including looking at how different escape gap sizes affect escape rates.
The work forms part of the Centre for Research-based Innovation Dsolve and the UArctic project Networking for increasing sustainability in snow crab fisheries in the Arctic.
Read the paper, published in Fisheries Research.