Damage from Bottom Trawling on Chilean Seamounts Still Visible More Than 25 Years Later, Study Finds

More than two decades after bottom trawling ended on the seamounts surrounding Chile’s Juan Fernández Archipelago, the damage it caused is still visible. A new study published in Deep-Sea Research provides the first scientific evidence from Chile of the long-term ecological toll of bottom trawling on deep-sea ecosystems.

The study was led by scientists from Oceana, the Center for the Ecology and Sustainable Management of Oceanic Islands, the Center for Advanced Studies in Arid Zones, together with researchers from several other national and international institutions. The team surveyed four seamounts using the remotely operated vehicle (ROV) SuBastian aboard the Schmidt Ocean Institute’s research vessel R/V Falkor during a 2024 expedition.

Researchers compared three seamounts with a history of bottom trawling to a fourth, ecologically similar seamount, known as Solito, where no evidence of bottom trawling has ever been recorded.

The contrast was stark. Solito is home to thriving deep-sea coral gardens, abundant sponges, and a rich diversity of invertebrates. The previously trawled seamounts, by comparison, showed lower live coral cover, reduced biodiversity, simplified habitat structure, and clear signs of seafloor disturbance — even after more than 25 years without any trawling activity.

“This study demonstrates that the impacts of bottom trawling on deep-sea ecosystems can persist for decades,” said Dr. Ignacio Petit, Oceana scientist and lead author of the study. “Although fishing ended more than 25 years ago, recovery remains extremely limited because many affected species, particularly deep-sea corals, grow very slowly and can live for hundreds, or even thousands, of years.”

Deep-sea corals play a critical role as ecosystem engineers. Their complex three-dimensional structures provide shelter, feeding grounds, and nursery habitat for numerous fish and invertebrate species. Yet those same corals, built up over centuries, can be destroyed by bottom trawling in a matter of hours.

“The presence of living corals supports higher invertebrate biomass, including commercially valuable crustaceans such as the Chilean golden crab (Chaceon chilensis) and the Juan Fernández spiny lobster (Projasus bahamondei). Conserving seamount ecosystems therefore also helps sustain local artisanal fisheries,” said Dr. Javier Sellanes, co-author of the study.

• Researchers surveyed four seamounts off the Chilean coast using a remotely operated underwater vehicle at depths exceeding 700 meters.
  
  
• This is the first scientific assessment in Chile of the long-term effects of bottom trawling on seamount ecosystems.
  
  
• More than 25 years after bottom trawling stopped in the area, the affected ecosystems still show clear signs of degradation.
  
  
• In 2012, Chile banned bottom trawling on 117 seamounts, establishing itself as a global leader in protecting these vulnerable marine habitats.
  
  

The findings are particularly significant for Chile, one of the first countries in the world to prohibit bottom trawling on seamounts. National legislation passed in 2012 protected 117 seamounts, recognizing the ecological vulnerability of these unique deep-sea habitats.

“The evidence confirms that protecting these ecosystems before they are damaged is by far the most effective conservation strategy. In environments where natural recovery may take centuries, preventing degradation is not only an environmental imperative but also an investment in the future of marine biodiversity,” Dr. Petit added.

Dr. Sellanes noted that under the Food and Agriculture Organization of the United Nations (FAO) guidelines for deep-sea fisheries, impacts lasting longer than five to 20 years are classified as significant adverse impacts.

“Our findings show that the Juan Fernández seamounts have far exceeded that threshold, with ecological degradation persisting for more than 25 years,” Dr. Sellanes said.

Bottom trawling continues in parts of Chile, targeting several species of hake and commercially valuable crustaceans. The new findings add further scientific weight to calls for precautionary management and the protection of vulnerable deep-sea ecosystems before they are irreversibly altered.