In the North Sea, commercial pelagic trawlers and seals both forage for some of the same fish stocks, creating a dynamic that can pose operational, regulatory, and conservation challenges.
To mitigate the issue, fishing industry groups have teamed up with fishing gear firms to develop and adapt excluder devices, aiming to reduce seal captures in the region’s sandeel and herring fisheries, as well as bycatch of other species.
A recent study, titled “Industry-led mitigation of seal bycatch in North Sea pelagic trawl fisheries: Evaluating excluder device effectiveness and policy implications,” evaluated the effectiveness of two seal excluder devices – an excluder tube reconfigured in collaboration with the Danish Pelagic Producers Organization (DPPO) and an excluder grid developed for use by members of the Pelagic Freezer Trawler Association (PFA).
Researchers referenced “spatially explicit, industry-led self-reporting bycatch data” to identify bycatch hotspots and were able to quantify a reduction in seal captures of 85 percent in the North Sea sandeel fishery and an estimated 89 percent in the herring fishery when excluders were used, though they “[acknowledged] broader uncertainty around the latter estimate.”
“These findings demonstrate the potential of gear-based mitigation to address marine mammal bycatch in high-risk areas,” the study said. “The datasets used are unique in their origin, representing voluntary, operational-level reporting by fishers with exceptionally high coverage of the respective fisheries. This collaboration between researchers and industry not only enhances data quality and quantity but also fosters stakeholder ownership, which is critical for policy acceptance and [uptake] of conservation measures. Our results support the continued and potentially mandatory use of excluder devices in areas of elevated bycatch risk, contributing to ecosystem-based fisheries management and marine mammal protection.”
The excluder tube, developed by DPPO with contributions from Egersund Danmark and Greenline Fishing Gear, was originally crafted to reduce bycatch of herring, mackerel, and gadoids in the Norwegian pout fishery before being adapted for the North Sea sandeel fishery. The device has been proven to reduce mackerel and haddock bycatch in the sandeel fishery and is now “assumed to reduce seal bycatch, as well,” the study noted.
DPPO said the research and its findings have reaffirmed the importance of collaboration across fishery stakeholders.
“When fishers and scientists work together, we can develop practical solutions that benefit both fisheries and the marine environment. The research is based on detailed data voluntarily collected and reported by fishers themselves, demonstrating the important role the fishing industry can play in generating scientific knowledge and developing effective solutions,” the organization wrote in a LinkedIn post celebrating the paper’s publication, adding that it is “proud to see industry-led innovation making a real difference.”
Meanwhile, the excluder grid, developed by PFA and Maritiem Net Manufacturing, was designed specifically for seals. The marine mammals are unable to pass through the semi-flexible grid apparatus installed at the point where the trawl net narrows and are, therefore, guided toward an outlet, while smaller target fish can easily swim through.
According to the study, the findings “intersect with broader policy developments” playing out across the E.U. and beyond.
“Overall, our results demonstrate that industry-led innovation can deliver durable and effective bycatch mitigation. The recent approval of the PFA excluder grid as compliant with E.U. technical measures illustrates how such bottom-up initiatives can be integrated into formal management. Embedding excluder devices within spatially targeted, adaptive management frameworks would represent a practical and immediately actionable step toward reducing marine mammal bycatch while maintaining viable pelagic fisheries,” they said.
The study’s authors include lead author Karin van der Reijden – who is affiliated with the National Institute of Aquatic Resources (DTU AQUA), the International Council for the Exploration of the Sea (ICES), and van der Reijden Marine Ecology and Fisheries – as well as Mollie Brooks, Ole Eigaard, Lotte Kindt-Larsen, and Mathias Søgaard of DTU AQUA; Niels Hintzen of PFA; and Claus Reedtz Sparrevohn and Emil Bundgaard Holm of DPPO.
Additional support for the research also came courtesy of the E.U.-funded CIBBRiNA project and the Danish Ministry of Food, Agriculture, and Fisheries through the Danish Green Development and Demonstration Program under the MiniMakS project, DPPO said.
“For us, this is another example of how research, innovation, and practical experience can go hand in hand in making fisheries more responsible and sustainable,” DPPO said.
