Bottom trawling is a destructive commercial fishing method that drags heavy, weighted nets across the seafloor, causing extensive and long-lasting damage to marine ecosystems.
Impacts include destruction of benthic (seafloor) habitats, reduced biodiversity, significant bycatch, and release of carbon from stored sediments. It is one of the most damaging ways to take fish from the ocean.
Bottom trawling is a fishing method that drags heavy, weighted nets across or close to the seafloor to catch fish and other marine species.
To catch target species, deep-sea bottom trawl vessels tow large nets fitted with steel doors, chains, and heavy rollers across (or close to) the seafloor. This equipment damages or destroys everything in its path, including slow-growing corals, sponges, and other habitat-forming species that provide essential breeding and feeding grounds and migratory waypoints for marine life.
Marine life caught unintentionally is called bycatch. It is one of the most destructive ways to catch fish.
Once destroyed, scientific evidence shows vulnerable marine ecosystems may take decades to centuries to recover, if they recover at all.
Seamounts are underwater mountains that rise from the deep ocean floor, often hundreds or thousands of metres. They are among the most biologically diverse environments in the ocean – and bottom trawling has been identified by the UN World Ocean Assessment as the “greatest current threat to seamount ecosystems.”
Cold, nutrient-rich water wells up around their slopes, concentrating life. Seamounts sustain dense communities of coral, sponges and fish, and act as oases for migratory species such as sharks and whales – fixed stations along their journeys where they feed, breed, spawn, rest and navigate. Many species found there are slow-growing, long-lived and some are found nowhere else, which makes these ecosystems both irreplaceable and highly vulnerable.
Because seamounts attract fish, they also attract fishing vessels, and because bottom trawling is indiscriminate, the coral and sponge communities that make seamounts so vital to ocean health are frequently destroyed in the process.
There are close to 2,000 seamounts in New Zealand waters.*
New Zealand is now the only country still bottom trawling in the South Pacific high seas, and it is a fishery that is mainly focused on seamounts.
* The New Zealand government keeps a SEAMOUNT database of all known seamounts and similar features (knolls and hills), which share many of the environmental characteristics of larger features. The latest update notes that many studies now use the more ecological term of ‘seamount’ for all features with an elevation of 100 meters or more, which we do here.
The impact of bottom trawling on vulnerable marine ecosystems includes –
Benthic (seafloor) habitats – Ancient coral gardens, sponge fields and biogenic reef structures are physically flattened by trawl gear. These habitats can take centuries to form and stabilise the seabed, cycle nutrients and support the food webs that keep the ocean healthy.
Biodiversity – Seamounts and other deep-sea features are among the most biodiverse and vulnerable ecosystems in the ocean – ecological home or migratory oases to unique species. These habitats are highly sensitive to disturbance, and even a single trawl can cause serious damage, and as few as ten trawls can reduce a coral habitat to rubble.
Bycatch of protected species – Latest data released by MPI to March 2026, reporting coral bycatch from the fishing industry shows that commercial trawlers caught 35,640kg of protected corals and sponges within New Zealand waters between October 2019 and March 2026.
Bottom trawling destroys fisheries – bottom trawling in critical habitats for a fish species can spell disaster for the fishery itself. New Zealand’s largest orange roughy fishery, the East and South Chatham Rise, has been trawled until just 8-18% of the fish population remains. Some orange roughy fisheries were already trawled to collapse and never re-opened.
Scientific evidence shows that recovery of damaged deep-sea environments, including seamounts, can take decades to centuries, if it occurs at all.
The UN’s World Ocean Assessment III (released 8 June 2026) cites studies of bottom trawling impacts on benthic communities, including from New Zealand’s Graveyard knolls and Tasmanian seamounts. It shows first signs of stony coral recovery only 15–20 years after fishing stopped.
New Zealand is guardian to one of the largest ocean territories on Earth – roughly 4 million km² and about 15 times its landmass.
Yet despite being an innovative maritime nation, New Zealand’s fishing industry continues to heavily rely on bottom trawling. Around 68% of New Zealand’s total commercial catch involves methods that contact or closely interact with the seafloor. The government’s own report, Our Marine Environment 2025, documents the lasting impacts of trawling and dredging on the seabed – altering seabed structure, damaging habitats and reducing marine populations.
Public concern about bottom trawling is strong and growing. Polling conducted by Horizon Research in April 2026 found that 90% of New Zealanders support limiting bottom trawling in some form. The survey also found that 47% of New Zealanders now identify bottom trawling as the greatest threat to the marine environment, up from 37% in comparable polling in 2024.
In 2026, the Swim4TheOcean petition attracted 73,647 verified signatures, making it one of the largest ocean-related petitions presented to Parliament in recent years.
That effort was built on years of work by organisations and individuals advocating for stronger ocean protection, including a 2020 petition led by the Deep Sea Conservation Coalition and conservation partners, which attracted 52,443 signatures.
The direction of public sentiment is clear: New Zealanders expect stronger ocean protection and a change in destructive fishing methods to protect vulnerable marine environments.
No. A call to end bottom trawling is not an anti-commercial-fishing position. It is about ending the kind of fishing that permanently damages the ocean floor, starting with seamounts.
The economic case for change is strengthening: the value of fish taken by trawling on seamounts is relatively small.
Meanwhile, a key seamount species, orange roughy, has been fished to an estimated 8-18% of unfished biomass on the Chatham Rise, prompting the government to halve the allowable catch and introduce an annual six-week closure of its breeding grounds.
In 2026, ocean champion and ultramarathon swimmer Jono Ridler swam 1,367km down the length of the North Island. It was a Swim4TheOcean aimed at highlighting the importance of a healthy ocean for Aotearoa New Zealand, with a clear call to end bottom trawling, starting with seamounts.
Jono, together with Live Ocean co-founder Blair Tuke, delivered a petition to Parliament signed by 73,647 people followed by a written submission.
Together with Jono Ridler, and on behalf of the 73,647 people who signed it, Live Ocean petitioned Parliament for three clear, achievable steps – and continues to call for them:
Aotearoa New Zealand has historically positioned itself as a global leader with a ‘clean, green’ brand. Yet our position on bottom trawling, particularly on seamounts, is becoming increasingly difficult to defend.
New Zealand is party to a growing number of international agreements, resolutions and commitments aimed at protecting vulnerable marine ecosystems in areas beyond national jurisdiction from destructive fishing practices.
While New Zealand is party to the UNGA and CMS resolutions, over the past twelve months New Zealand has failed to commit to the High Seas Treaty (BBNJ) ratification or join the 97% of IUCN membership that voted for the Seamount protection resolution.
While New Zealand falters, the world’s ocean nations are signaling their commitment to the protection of seamounts and other marine ecosystems from destructive fishing practices like bottom trawling.
Already a number of fishing nations have moved towards partial or complete restrictions on bottom trawling on vulnerable habitats.
Most notably, New Zealand is now the only country continuing to issue licenses for bottom trawling on seamounts in the South Pacific high seas. This places New Zealand increasingly at odds with both international expectations and the direction of global ocean governance.
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