Understanding Bottom Trawling and Its Widespread Use in European Waters

Bottom trawling, a commercial fishing method where large nets equipped with heavy metal doors and ground chains are dragged along the seafloor, has been a staple in Europe's fishing industry for decades. This technique targets demersal species like cod, haddock, and flatfish by scraping the ocean bottom, but it also disrupts marine habitats, stirs up sediments, and captures unintended marine life. In European Union waters, along with those of the UK, Norway, and Iceland, over 4,900 bottom trawlers operate annually, logging more than 5.5 million hours of fishing time. This extensive activity covers vast areas, with some regions seeing over half their seabed trawled each year.

The practice supports a portion of Europe's seafood supply, contributing roughly 2 percent of the continent's animal protein from marine sources. It directly employs fewer than 20,000 people, though indirect jobs in processing and supply chains expand this figure. However, growing concerns about its sustainability have prompted researchers to quantify not just ecological harm but also the full economic picture, revealing hidden costs borne by society at large.

A Landmark Peer-Reviewed Study Emerges

Published on April 28, 2026, in the journal Ocean & Coastal Management, the paper titled "The value of bottom trawling in Europe" provides the first comprehensive assessment of the practice's net societal value. Led by marine scientist Katherine D. Millage of National Geographic Pristine Seas, the study integrates data on fishing effort, economic outputs, subsidies, and environmental externalities. It employs a full economic valuation framework, accounting for both market-based benefits like revenue and non-market costs such as climate impacts.

By analyzing vessel tracking data from 2016 to 2021, the researchers calculated private profits to the industry at approximately €180 million annually. Yet, when factoring in societal costs, the balance shifts dramatically to a net loss ranging from €2.07 billion to €15.97 billion per year—up to 90 times the industry's gains. This disparity underscores a key tension: while bottom trawling delivers short-term private benefits, it imposes long-term burdens on taxpayers, ecosystems, and future generations.

Academic Researchers Driving Marine Policy Insights

The study's multidisciplinary team draws from leading academic institutions, highlighting higher education's role in informing ocean governance. Co-author U. Rashid Sumaila, an ocean and fisheries economist at the University of British Columbia, emphasizes the need for broader cost-benefit analyses in policy. Trisha B. Atwood from Utah State University contributes expertise on carbon dynamics, while collaborators like Maria L.D. Palomares bring fisheries biology perspectives.

These scholars, affiliated with National Geographic Pristine Seas and various universities, exemplify how higher education bridges science and decision-making. Their work not only quantifies impacts but also simulates scenarios for reduction, showing that halving bottom trawling effort could yield net societal gains by restoring fish stocks and curbing emissions. Such research positions universities as pivotal in training the next generation of marine scientists and policymakers.

Dissecting the Economic Breakdown

To grasp the scale, consider the study's detailed ledger. Private sector benefits include €2.46 billion from protein supply value and €1.78 billion from labor contributions tied to jobs. However, costs dominate: fuel and operations strain budgets, with €220 million lost to discarded catch—75 percent of what is hauled up, including juveniles and non-target species like sharks and corals.

This table illustrates how climate-related externalities tip the scales. Governments provide €1.17 billion in fuel subsidies yearly, propping up an industry unprofitable without them in nations like Belgium and Spain. Redirecting even a fraction could fund transitions to sustainable methods.

Climate Costs: The Seafloor Carbon Bombshell

A pivotal revelation is bottom trawling's climate footprint. Disturbing seabed sediments releases organic carbon stored for centuries, with European-flagged vessels emitting 112 million metric tons of CO2-equivalent annually—nearly a third of global trawling emissions (370 million tons). Valued at conservative social cost rates, this alone costs society €4.87 billion to €18.15 billion yearly. The full study details these calculations, drawing on sediment remineralization models.

This positions bottom trawling as a significant contributor to atmospheric CO2, comparable in scale to sectors under intense scrutiny. Recovery post-ban, as seen in the UK's Lyme Bay—where reef species surged 95 percent and juvenile lobsters 400 percent—suggests restoration could sequester carbon anew.

Subsidies Fueling an Uneconomic Practice

European taxpayers foot €1.17 billion annually in fuel subsidies for bottom trawlers, ostensibly for food security and jobs. Yet, the study reveals these props mask underlying losses: half the Dutch fleet idled amid 2026 fuel spikes. Small-scale fisheries, employing three times more people with lower impacts, offer a viable contrast. Phasing out subsidies could incentivize selective gears and static methods like pots or traps, enhancing profitability and resilience.

Intrusion into Marine Protected Areas

Alarmingly, 23.2 percent of bottom trawling effort occurs within Europe's 6,000 MPAs, spanning 900,000 square kilometers. In 59 percent of EU MPAs, intensity is 1.4 times higher than outside, undermining biodiversity goals. Countries like France and Spain exceed 25 percent MPA effort. A ban here aligns with the EU's 30x30 target, potentially spilling over benefits to adjacent fisheries via enhanced stocks.

Scientific Debate and Methodological Critiques

While influential, the study faces pushback. Critics, including Prof. Jan Hiddink of Bangor University and ocean biogeochemists, argue the carbon remineralization model overestimates emissions by 100-1,000 times, relying on disputed parameters from prior work. Without these, net losses shrink to modest figures. They highlight unaddressed counterfactuals, like food displacement to land-based proteins with higher emissions, and innovations reducing impacts. This analysis calls for refined models incorporating management successes.

Balanced discourse strengthens science, urging replication and empirical validation. Higher education plays a key role, fostering debates that refine policy tools.

Sustainable Alternatives and Transition Pathways

• Static gears (pots, traps): Lower bycatch, minimal habitat damage.
• Selective trawls: Modified nets reducing juveniles and non-targets.
• Small-scale fisheries: Triple employment, sustainable yields.
• MPA enforcement: Greece's 2030 ban pledge sets precedent.

Simulations show halving effort boosts net benefits, restoring overfished stocks. Investments in gear tech and training could ease transitions, creating jobs in green fisheries.

Implications for Marine Science Careers and Policy

This research spotlights opportunities in higher education for marine economists, ecologists, and modelers. Universities like UBC exemplify programs training experts for ocean challenges. Policymakers eye subsidy reforms and MPA protections, with the EU plan targeting phase-outs by 2030. Forward-looking strategies promise healthier seas, economic stability, and climate mitigation.

Stakeholders—from fishers to academics—must collaborate for equitable shifts, ensuring Europe's blue economy thrives sustainably.

Photo by ARTISTIC FRAMES on Unsplash