Bottom trawling damage revealed: 128 new species end up as by-catch

Monday, 2 August 2021

A catch of orange roughy is hauled aboard NZ deep sea trawler Corsair in the Tasman Sea (file photo).

Up to 5000 tonnes of coral, some likely more than two millenniums old, was scraped off the sea floor by bottom trawling nets in one year alone, a new report has revealed.

On Thursday morning, New Zealand conservation groups who collected 52,000 signatures calling for a ban on bottom trawling on seamounts will present to the Government’s Environment Select Committee on the impact of bottom trawling in New Zealand waters.

Researchers from the Deep Sea Conservation Coalition – an international collective of more than 80 non-government organisations, fishery groups, and law and policy institutes – will present a prepared report to the committee.

Bottom trawling is a fishing practice where weighted nets are dragged along seamounts to scoop up fish like orange roughy.

A graphic from the Deep Sea Conservation Coalition illustrating what bottom trawling is.

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It has been the subject of some controversy, often due to the undersea species that end up as by-catch.

Some of the report’s key findings hinge on those species.

Researchers found over the last three years, Kiwi scientists identified 128 new-to-science species from fishery by-catch, during the course of a marine invertebrate identification project.

Greenpeace used paint and lights to get their message against bottom trawling across at Port Nelson.

Many had been found on or around seamounts.

The report also found more than 14 tonnes of corals were dragged up by the New Zealand fleet’s bottom trawling nets in the 2018-19 year alone.

But only a fraction of coral destroyed made it to the surface, researchers said It was estimated that 14 tonnes of coral in nets meant 1515 to 4769 tonnes had been destroyed on the seabed.

Scientists said many of the seamounts in New Zealand’s exclusive economic zone (EEZ) were hotspots for biodiversity, including many ancient, slow-to-reproduce species.

Coral samples from areas used for fishing identified black coral up to 2600 years old, and bubblegum coral up to 500 years old. Orange roughy, the main fish species trawled for on seamounts, could themselves live up to 220 years.

Significantly, the report also found all six New Zealand vessels currently permitted to bottom trawl in the South Pacific high seas belonged to companies that had been convicted of illegally fishing in closed areas in the past year.

The Department of Conservation estimated 85 per cent of New Zealand’s wildlife was in the ocean, and New Zealand had more than 800 biodiversity-rich seamounts in its EEZ alone.

Report author Karli Thomas said the report showed how significant they really were.

Greenpeace ocean campaigner Jessica Desmond outside Parliament. (File photo)

“These studies confirm that many of our deep water coral forests have been growing for hundreds or even thousands of years, but a single bottom trawl can destroy them in minutes.

“The Ministry for Primary Industries is busy trying to calculate how many seamounts it is OK to destroy, to try and justify our fleet’s continued rampage, rather than focussing on ocean protection and our international obligations. It’s time for the minister to rein them in.”

Conservation groups presenting to the Environment Select Committee this week agreed.

Greenpeace ocean campaigner Jessica Desmond said the Government needed to put protecting deep sea life before the interests of commercial fishing.

“Time is running out to safeguard the biodiversity of the ocean. This report shows the widespread destruction caused by bottom trawling seamounts – it’s time the minister stepped in to ban it.”

Livia Esterhazy from the World Wildlife Foundation NZ said intervention was “well overdue”.

“We know these fragile coral forests take decades to even start recovering from bottom trawling.

“The government urgently needs to prioritise Aotearoa’s incredible marine biodiversity and ban bottom trawling on seamounts now.”

Forest & Bird’s Geoff Keey said the Government had adopted a biodiversity strategy that sought to turn around the biodiversity crisis, including increasing marine protections, reducing by-catch to zero, and moving to ecosystem-based management of fisheries.

“The destruction caused by bottom trawling is completely unsustainable.”

Fisheries New Zealand fisheries management director Emma Taylor said it was incorrect to suggest the organisation did not care about ocean protection and its international obligations.

'Fisheries New Zealand closely monitors bottom trawling as part of a comprehensive fisheries management system. Controls on bottom trawling include closed areas, regular monitoring of where vessels have fished, and the type and quantity of marine species caught.'

Fisheries New Zealand was in the process of completing 'comprehensive' research on bottom trawling and its impacts on marine biodiversity, she said.

About 1.2 million square kilometres of seabed habitat in New Zealand waters is closed to bottom trawling.

The annual trawl footprint had reduced over time and the trawl effort was typically over areas that had already been trawled, Taylor said.