A growing debate over bottom trawling is putting the future of Aotearoa’s marine environment under the spotlight, with scientists warning that the fishing method can have significant and long-lasting impacts on ocean ecosystems.
The issue has re-emerged following discussions around proposed fisheries reforms and comments from political leaders suggesting the economic benefits of bottom trawling must be balanced against environmental concerns. Marine scientists say the evidence shows the impacts extend far beyond the fish being caught.
What Is Bottom Trawling?
Bottom trawling involves dragging large weighted nets across the seafloor to catch fish and seafood species that live near the ocean bottom.
The method is widely used around the world and remains an important part of commercial fishing operations, including in New Zealand waters. Species commonly caught through bottom trawling include hoki, hake, orange roughy, squid, prawns and other deepwater fish. Around a quarter of the world’s wild-caught seafood is harvested using bottom trawling methods.
Supporters argue it is one of the most efficient ways to harvest large quantities of seafood and helps support jobs, exports and food production.
Marine ecologists say the environmental cost can be substantial.
Research highlighted by the Science Media Centre shows that when trawl nets move across the seafloor they kill, displace and disturb animals living within marine sediments. The process can reduce biodiversity, alter habitat structure and change the way nutrients and carbon are processed within ocean ecosystems.
Scientists describe the seafloor as one of the planet’s most important natural systems, playing a critical role in cycling carbon and nitrogen and supporting marine food webs.
Repeated trawling can favour smaller, fast-growing species while reducing populations of larger and more vulnerable organisms that help maintain healthy ecosystems.
Environmental groups compare the practice to bulldozing a native forest, arguing that damage to deep-sea coral communities and seamount ecosystems can take decades or even centuries to recover.
One of the most significant emerging concerns involves the role of the seabed in storing carbon.
Scientists say marine sediments represent the largest carbon store on Earth. When heavy fishing gear disturbs these sediments, carbon that has been locked away for long periods can be released back into the water column and potentially the atmosphere.
Researchers are increasingly investigating how bottom trawling contributes to carbon emissions and whether reducing seabed disturbance could support climate change mitigation efforts.
For a country committed to reducing emissions and protecting biodiversity, the issue is becoming increasingly important.
Bottom trawling is also criticised for its bycatch impacts.
Because the nets can be relatively indiscriminate, non-target species including corals, sponges, sharks, seabirds, dolphins and other marine animals can be caught or harmed during fishing operations.
Scientists note that vulnerable deep-sea habitats often support a wide range of species and that damage to those ecosystems can affect marine biodiversity far beyond the immediate fishing area.
New Zealand remains one of a small number of nations that continue to permit bottom trawling in parts of the South Pacific and within domestic waters. The practice is particularly associated with deepwater fisheries targeting species such as orange roughy and oreo.
The debate has become increasingly prominent as conservation groups, iwi, environmental organisations and marine scientists call for stronger protections for sensitive marine habitats and seamount ecosystems.
Many Māori communities have long advocated for sustainable fisheries management grounded in kaitiakitanga and the protection of marine taonga for future generations.
For iwi and hapū with strong connections to the moana, concerns about seabed degradation are often viewed through both environmental and cultural lenses.
The challenge facing policymakers is balancing environmental protection with the economic importance of the fishing industry.
Commercial fisheries contribute significantly to New Zealand’s economy and support employment in many coastal communities. Industry representatives argue that modern fisheries management, monitoring and spatial protections can reduce environmental impacts while maintaining seafood production.
However, scientists say evidence increasingly points to the need for greater caution when managing vulnerable marine ecosystems.
As New Zealand continues to debate the future of fisheries management, bottom trawling is emerging as one of the most contentious issues.
For some, it remains an essential fishing tool that supports regional economies and food production.
For others, it represents an outdated practice that risks damaging ecosystems that cannot easily be restored.
What is clear is that the conversation is no longer solely about fish stocks. It is increasingly about biodiversity, climate change, cultural values and how Aotearoa chooses to protect the health of its oceans for future generations.
image: https://education.nationalgeographic.org/resource/impacts-bottom-trawling/ – image recast for our Aotearoa audience
