Two groundbreaking studies to move away from destructive fishing practices and end underwater deforestation

25 March 2025

A few weeks before the third United Nations Ocean Conference hosted by France in Nice (UNOC 3), BLOOM has released a major report entitled “Breaking free from Trawling,” based on the results of over a year of research conducted by scientists from L’Institut Agro and the National Museum of Natural History in France. This work demonstrates that it is technically possible to move away from destructive fishing methods: in France, 85% of the fish volumes caught by bottom trawlers could be harvested using far less impactful fishing techniques such as lines, traps, and nets. The report also calculates, for the first time, the cumulative impact of the approximately 800 French bottom trawlers, which collectively destroy 670,000 km² each year. 

Additionally, BLOOM publishes an original scientific comparison demonstrating that the deforestation of marine ecosystems caused by bottom trawling is 20 to 47 times greater than terrestrial deforestation. The study estimates that more than half of this marine deforestation occurs in Europe, covering over 2 million km², nearly a quarter of which (400,000 km²) falls within so-called “protected” marine areas. 

Breaking free from trawling: It’s Possible ! 

The report “Breaking free from Trawling”, based on the findings of scientists from L’Institut Agro (Didier Gascuel, Florian Quemper, Romain Mouillard) and the National Museum of Natural History (Harold Levrel), makes phasing-out of bottom trawlers an achievable reality. The researchers demonstrate that in France, 85% of the fish volumes caught by bottom trawlers on vessels of less than 40metres long – still allowed in so-called “protected” marine areas – could be harvested using much less impactful fishing techniques known as “passive gears.” It also establishes the destructiveness of this fishing technique that scrapes the ocean floor over an area equivalent to the combined size of France, Switzerland, and Belgium, devastating both marine fauna and flora along its path. 

BLOOM’s report also highlights that bottom trawling has the worst environmental and economic footprint of all the methods used by French fishing fleets. Yet, trawlers and seine nets receive over 75% of public subsidies. Without these government subsidies, most of these fleets would not be profitable. The tragic conclusion is clear: in France, the fishing industry that creates the fewest jobs and has the most detrimental impact on the ocean is the one that the government continues to support at all costs. 

>>>Read the full report “Breaking free from trawling.” <<<

An inevitable deregistration of trawlers despite the state’s relentless support. 

Despite public subsidies, the bottom trawler model is doomed: trawler deregistration has already begun, and trawler catches have been in sharp decline for the past fifteen years. With political will, this process of decline could have been anticipated, and the transition organized through a policy of converting destructive practices to passive fishing gears. Through the strategic sector contract, 700 million euros were allocated to continue the recipe for disaster and encourage the industrialization of the sector. President Emmanuel Macron has chosen the path of techno-solutionism, which will inevitably contribute to increasing fishing effort and pressure on ecosystems, thus ignoring all scientific recommendations. Instead, such a sum should have been used for a transition to truly sustainable fishing, one that minimizes its environmental impact, maximizes employment, and contributes to food sovereignty. 

BLOOM’s report and the researchers’ work show that we have in our hands the first elements needed to free fishermen and society from techniques that mechanically destroy both marine life and public finances. It is high time that decision-makers take action and develop a transition plan for the sector that matches the ongoing social and ecological crisis. 

The Portrait of Trawling: A Combination of Flaws 

By analyzing the impact of fishing fleets (operating in the Mediterranean, North-East Atlantic, and conducting “distant” fisheries) across 10 social, ecological, and economic indicators, the researchers demonstrate that trawling, particularly bottom trawling, is the most destructive practice. 

• Combined, pelagic and bottom trawls account for over 60% of the landed volumes, despite representing only 13% of the vessels. 

• Bottom trawlers alone represent 11% of the fleet but are responsible for 25.5% of the landed volumes. 

• Trawlers are responsible for 88% of overexploited resources. 

• They hinder the renewal of fish generations: more than one in two juvenile fish caught comes from trawlers. 

• They emit 77% of the CO₂ emissions from the French fishing fleet. 

• Bottom trawlers have a particularly devastating footprint, responsible for 90% of the damage to the seabed caused by French fishing activities. 

• French bottom trawlers destroy an average of 670,000 km² of marine ecosystems each year. 

• One single pass of a bottom trawl kills between 20% and 50% of the invertebrates present in the area. 

• From a socio-economic perspective, large tuna purse seiners and pelagic trawlers, such as the Scombrus or Prins Bernhard, mega-industrial vessels producing fish paste, devastate coastal economies: they create 10 times fewer jobs than fleets using passive fishing gears. Pelagic trawlers over 40 meters create 3 to 4 times less value added per tonne of fish landed compared to coastal passive gear methods. 

Furthermore, using a recent estimate published in the scientific journal Nature, which places the global trawled area at 4.7 million km², BLOOM has released a scientific note showing that marine deforestation is 20 to 47 times greater than terrestrial deforestation in terms of surface area. The study estimates that more than half of this marine deforestation occurs in Europe, covering over 2 million km², with nearly a quarter (400,000 km²) located within its so-called “protected” marine areas. 

>>>Read our full report on marine deforestation <<<

In light of these results, the only inevitable conclusion is to break free from trawling, not its preservation. Breaking free from trawling is a necessity for life and the survival of small-scale coastal fishing. 

The first step in the transition of fisheries: breaking free from bottom trawlers. 

The end of bottom trawling is an obvious necessity. To support this transition, researchers have simulated a transfer of the volumes caught by bottom trawlers under 40 meters to passive fishing gears (traps, lines and nets) on vessels of the same size. This constant-volume transfer approach demonstrates, for the first time, that trawlers deregistration is feasible. Their results show that 85% of the volumes caught by trawlers can be transferred to passive fishing gears. Of the total volumes studied, 39% are even “easily transferable,” meaning that redirecting quotas allocated to bottom trawlers towards traps, lines, and nets would allow us to source species such as monkfish, hake, common sole, bass, and conger without destroying ecosystems. 

Currently, fishing quotas are mostly controlled by industrial fishing operations due to the lack of effective implementation of Article 17 of the Common Fisheries Policy, which clearly states that member States shall use transparent and objective criteria, including environmental, social, and economic criteria. 

Trawler deregistration is a key piece of the puzzle for the social-ecological transition of fisheries. Truly sustainable fishing will only be possible if various levers are activated, all of which aim to minimize the environmental impact of fishing while also creating jobs. It has become urgent to: 

• Ensure the protection of juvenile fish to rebuild populations and the resilience of ecosystems; 

• Sanctuary the coastal zone for vessels under 25 meters; 

• Relocalize production by dismantling industrial giants; 

• Establish genuinely protected marine areas; 

• Finance the transition and anticipate the transformation of the sector. 

Protecting the ocean is simple; we just need to stop destroying it.