New Study Torpedoes The Case Against Bottom Trawling

Global Study Backs Trawling And Dredging, ⁠‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌⁠And Exposes The Data Gap Behind The “Destructive Fishing” Label

A major international review of demersal trawling and dredging, published this month in the journal Fish and Fisheries, hands the fishing industry some of its strongest scientific backing in years, while quietly dismantling the case environmental campaigners routinely make against these gears.

The paper, “Challenges and Opportunities for Strengthening Bottom-Tow Fisheries Sustainability“, comes from a 33-strong international working group of scientists, fisheries managers and industry representatives, convened at the 2024 World Fisheries Congress in Seattle. Its authors favour the term “bottom-tow” as an academic umbrella for trawls and dredges. It is not a term any working commercial fisherman would recognise, and The Skipper sees no reason to adopt it. What follows uses the term commercial fishermen actually use: demersal or bottom trawling and dredging.

A STUDY BUILT WITH COMMERCIAL FISHERMEN, NOT AGAINST THEM

The first thing worth noting is who wrote this. The author list spans NOAA’s Alaska and Northwest Fisheries Science Centers, the University of Washington, Heriot-Watt University, ICES, the Alaska Seafood Cooperative, United Catcher Boats and Trident Seafoods, alongside university researchers and conservation groups. This was not an NGO-commissioned report built to justify restriction. Fishing industry participants had equal say in identifying both the problems and the fixes, which means the conclusions cannot be waved away as either campaign literature or industry lobbying dressed up as science.

A 24-MILLION-TONNE FOOD SOURCE THE CAMPAIGNS RARELY MENTION

The paper opens by putting a number on what is actually at stake: demersal trawl and dredge gear lands roughly 24 million tonnes of seafood a year, a major share of the world’s wild-caught animal-sourced food supply. With the global population heading towards 10 billion within three decades, the authors are blunt that failing to keep these fisheries viable simply shifts food production onto land-based systems and other proteins, which carry their own, often larger, ecosystem footprints. That framing, fishing as food production with tradeoffs to be managed rather than an activity to be eliminated, sits at the heart of the paper’s concluding argument, and it is one The Skipper would encourage commercial fishermen to borrow directly when making the case to politicians and the public.

THE CERTIFICATION NUMBER THAT UNDERCUTS THE “DESTRUCTIVE FISHING” LABEL

The authors point out that over a third of fisheries certified as sustainable by the Marine Stewardship Council, a globally recognised, independent standard, employ demersal trawl or dredge gear. That is a difficult fact for any campaign built on the premise that demersal trawling and dredging are inherently incompatible with sustainability. The paper cites separate published research describing “destructive fishing” as a term that is used constantly in media, academic and policy discourse while remaining vague and inconsistently defined. In other words, the label gets used as a verdict when it has never really been defined as a standard.

THE REAL FINDING: A DATA PROBLEM, NOT A PROVEN PATTERN OF HARM

The study identifies 30 specific gaps blocking progress on sustainability. Read them closely and a pattern emerges: the overwhelming majority are gaps in data and measurement, not documented findings of damage. There are no reliable measurements of gear-to-seafloor contact across most gear types, maps of benthic habitats are largely unavailable, and discard mortality rates, the “unobserved mortality” campaigners increasingly cite as a reason to restrict fishing, are described as empirically unassessed in most fisheries.

This is the paper’s sharpest, if understated, ⁠‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌⁠rebuke to the environmental lobby: campaigns routinely present the absence of data as proof of harm, when the scientists studying this professionally say the honest position is that, in many fisheries, nobody, including the regulators, currently knows the true scale of impact. Precaution is one thing. Certainty dressed up as precaution is another, and this paper draws that line clearly.

CLOSURES ARE NOT THE SIMPLE FIX NGOs CLAIM

Given the live fights over Marine Protected Areas around Ireland’s coast and the six-mile zone, the paper’s verdict on spatial closures deserves attention. The authors warn that “time and space closures require enforcement to be effective” and that “the performance of closures are context dependent and may not achieve ecological and economic outcomes as effectively as desired… compared to other management approaches”, noting that badly designed closures can simply displace fishing effort into new areas, sometimes increasing bycatch elsewhere. For an industry facing a 30% ocean protection target and closure proposals routinely sold as straightforward conservation wins, that is a direct scientific challenge to the assumption that closing ground automatically delivers a benefit.

RED TAPE, NOT REFUSAL, IS WHAT IS SLOWING GEAR INNOVATION

One of the more pointed sections deals with gear innovation, an area where commercial fishermen are regularly accused of dragging their feet. The authors list genuine advances already in use or on trial across the fleet: sorting grids, bycatch escape panels, electrical stimulation devices, trawl lifting gear. But they say fishing gear innovation “has lagged” land-based food technology specifically because “experiments with fishing gear design or practices… often require navigating complicated regulatory processes to obtain permits, adding cost and slowing progress”. The barrier is bureaucracy, not a lack of will on the water, a more useful fact than the usual accusation that the industry refuses to change.

BLANKET RULES PUNISH THE FLEET THAT IS ALREADY DOING IT RIGHT

The paper also takes aim at how regulations are designed. It notes that “harvests and ecological performance in terms of bycatch and seabed impacts can vary substantially among fishers” and that failing to account for this “within-fleet heterogeneity” undermines the fairness and effectiveness of new rules. In plain terms: a blanket restriction penalises well-run vessels for the practices of the worst performers, while doing nothing to identify who is actually causing a problem, an argument commercial fishermen have made for years at consultation meetings, now with a peer-reviewed citation behind it.

NAMING NAMES: CLIENTEARTH, OCEANA AND ATTENBOROUGH’S OCEAN

The claims commercial fishermen are actually up against this year are specific, and worth answering directly. Sir David Attenborough’s Ocean, the Silverback Films and National Geographic documentary, tells audiences that trawling destroys an area of seafloor “nearly as large as the Amazon rainforest every year”, that it “releases up to 370 million metric tons of carbon dioxide into the atmosphere every year”, and that “over three quarters of a trawler’s catch may be thrown away”. ClientEarth’s own campaign material states that the practice “emits around 40% of annual U.S. transportation emissions” by destroying seagrass, and that unwanted catch “can make up to 60% of the total catches”. Oceana calls bottom trawling “one of the most destructive methods to catch fish”, one that will “effectively clear-cut everything living on the seafloor”.

Every one of those headline figures rests on exactly the kind of modelling the Sethi synthesis says the science does not yet support. On carbon, the paper states that “empirical measurements of carbon release from fishing gear disturbance are rare” and that the models used “to scale fishing-related disturbance to seascape scale carbon release may be inaccurate or uncertain”, citing the very 2023 Nature paper that formally challenged the inflated estimate underlying those carbon figures in the first place. On seafloor area and habitat loss, the study lists benthic habitat maps and seafloor disturbance frameworks as gaps “largely unavailable” in most fisheries, meaning claims about area destroyed rest on extrapolation, not measurement. On bycatch, the paper flags non-target catch accounting and discard mortality rates as similarly unaccounted for in many jurisdictions, precisely the standardised data that would be needed to stand behind a figure like “75% of the catch” or “60% of total catches” as anything more than a dramatic example generalised to an entire global fishery.

None of this means the documentary’s footage was faked or that the campaign groups are lying. It means, as independent fisheries scientists reviewing the same film have separately concluded, its dramatic scenes of scallop dredging and bycatch-heavy hauls are “not an accurate representation of bottom trawling globally”, because “sustainability is a function of management, not gear type” and “most bottom trawling occurs on sand, mud, and gravel”, not the coral gardens the cameras favour. It is also why over a third of MSC-certified fisheries, and more than 80 bottom trawl fisheries specifically, carry a sustainability label that Oceana’s “most destructive” framing cannot explain away.

WHAT IT MEANS FOR COMMERCIAL FISHERMEN

None of this hands the industry a free pass, and the paper does not pretend otherwise. Seafloor disturbance is real, bycatch is real, and the authors are explicit that governance is genuinely inadequate in some jurisdictions. But the debate commercial fishermen are actually facing, in cinemas, on campaign websites, and in courtrooms where ClientEarth and Oceana are currently pursuing the Spanish and Dutch governments over trawling in Marine Protected Areas, is not being fought on the terms this study supports. It is being fought on headline figures that a 33-strong, cross-disciplinary international review says the underlying science cannot yet stand behind.

That gives commercial fishermen something concrete to bring to the next consultation, the next quota negotiation, and the next primetime documentary that calls their livelihood destructive without being able to show its working. The industry does not need to deny its impact on the seabed to make that case. It needs only to ask campaigners and broadcasters the same question this peer-reviewed synthesis asks of the whole sector: where, precisely, is the data behind the number.

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