Key findings: A 26-year University of Gothenburg study finds limits on bottom trawling in Kosterhavet National Park have helped fish, shellfish and filter-feeders recover. Researchers used AI to analyze ROV footage from 1997–2023 and tracked 17 species across ~4.4 million images. While protections reduced fishing impacts and allowed many species to rebound, warming shallow waters are driving declines in large, heat-sensitive species that may need deeper refuges. The study shows protections work locally but highlights the need to address climate-driven change for full ecosystem recovery.
26-Year Study Shows Swedish Seabeds Rebounding After Trawling Limits — Warming Still Threatens Some Species
Key findings: A 26-year University of Gothenburg study finds limits on bottom trawling in Kosterhavet National Park have helped fish, shellfish and filter-feeders recover. Researchers used AI to analyze ROV footage from 1997–2023 and tracked 17 species across ~4.4 million images. While protections reduced fishing impacts and allowed many species to rebound, warming shallow waters are driving declines in large, heat-sensitive species that may need deeper refuges. The study shows protections work locally but highlights the need to address climate-driven change for full ecosystem recovery.
16:40, 04.11.2025Environment
Long-term protections help marine life recover, but climate warming poses new risks
A 26-year study led by researchers at the University of Gothenburg and published in Ecology and Evolution reports clear ecological improvements on the seabeds of Kosterhavet National Park after limits on bottom trawling were introduced. Fish and shellfish populations have increased, and filter-feeding organisms such as mussels, anemones and soft corals are noticeably more abundant where trawling has been restricted.
The research team analyzed underwater footage collected by a remotely operated vehicle (ROV) between 1997 and 2023. Using machine-learning tools, a student team member, Christian Nilsson, used an AI object-detection model to review selected clips and identify species traits. The model tracked 17 species across approximately 4.4 million images, transforming thousands of hours of video into a robust, long-term species timeline in just a few hours of processing.
Project lead Matthias Obst, a marine ecosystem researcher at the University of Gothenburg, explained why filter-feeders benefited:
“Animals that capture nutrients through filtration, such as mussels, anemones, and soft corals, do not thrive when bottom trawls stir up sediment from the seabed. Several of these species have recovered significantly.”
At the same time, the study highlights a contrasting trend: rising temperatures in shallow waters are reducing or eliminating some large, heat-sensitive species that play important roles in habitat structure and ecosystem function. Obst and colleagues note that while protected areas reduce fishing pressure, warming driven by climate change may force vulnerable species to move to deeper, cooler waters — or face local decline.
What this means
The findings demonstrate that targeted management measures, like trawling restrictions, can produce measurable ecological recovery. However, they also emphasize the limits of local protections in the face of global climate change. Conservation measures can restore habitat and help many species rebound, but they may need to be combined with broader climate mitigation and adaptive planning (for example, identifying deeper refuges for heat-sensitive species) to secure long-term resilience.
The paper places these results alongside other conservation successes — from assisted recoveries and rediscoveries of rare species to reintroductions — underscoring that effective management can produce positive outcomes, even as climate change creates new challenges.
Study details: University of Gothenburg; 26-year span (1997–2023); journal Ecology and Evolution; AI-assisted analysis of ~4.4 million images; 17 species tracked.