DEEP SEA TRAWLING – DESTROYING NEW HABITATS


By Roger Grace

Deep Sea Trawling

Deep Sea Trawling 2

top: A good catch of orange roughy and some bycatch species in the net of the Chinese-crewed trawler Chang Xing on the high seas in the Tasman Sea.

above: Selected bycatch discarded from the Chang Xing includes a lantern shark, several rattails, oilfish, dories, an urchin, and ghost sharks with bizarre snouts.

below: Unwanted fish and orange roughy heads were gobbled up by hoards of albatrosses and petrels numbering in their thousands.

Deep Sea Trawling 3

We’re at it again. Humans behaving badly. And the environment is what suffers because of the ignorance, greed or indifference of a small number of people. This time it is the deep sea being trashed.

Whenever humans move into a new environment, it is the exploiters who go there first, leaving a trail of destruction for others to follow. By the time anyone comes along with thoughts of conserving some of what is being destroyed, the best has already gone and we can only guess at what it would have been like in its pristine state.

Look at the history of any living resource and the story is the same. Whales, seals, forests, and fish. They are almost completely destroyed before conservation measures are attempted. And the exploiters argue with the conservationists and slow any serious moves at protection. Usually it is a case of far too little, far too late. It is rare for a resource to be adequately assessed upon its discovery, and a logical plan put in place conserving the best or most significant bits and carefully managing sustainable exploitation of the rest.

And so here we go again, this time in the deep sea. Fishing trawlers are dragging their huge heavy nets across the seafloor, smashing everything in their path in the quest for a few financially valuable species of fish. To hell with the other animals destroyed by the nets. No matter that some of them have taken hundreds of years to grow, and are an important part of the habitat in which the ‘valuable’ species live. Too bad if, after a few passes of the net, the habitat is no longer a suitable home for these fish species and they probably will never recover in several lifetimes. This is not sustainable fishing. This is strip-mining.

In this case the target species is orange roughy – a difficult species to manage sustainably at the best of times because of its age structure. They live to between 80 and 150 years, and don’t start breeding till they are 20 or 30 years old! How can you figure out a sustainable level of fishing for an animal that grows so old and is so slow to breed? Fisheries scientists reckon that if you fish the population down to 30% of the original biomass, then it can be fished ‘sustainably’ at that level. But the annual take would probably be uneconomical.

As with most commercially valuable species, in practise it is very difficult to back off fishing once the target level is reached. Despite the 30% level being enshrined in Quota Management System legislation, nearly all orange roughy stocks have been overfished to well below that level. Two fisheries were finally closed in recent years when they had been overfished down to 7% and 3% of their original biomass! They will never recover in the lifetimes of the fishermen who fished them out, or the Government bureaucrats who let it happen. Forest and Bird has recently released a guide for those who care enough to adjust their eating habits in favour of fish which have been caught with minimum impact on the environment. Unfortunately orange roughy rates the worst of 12 ‘bad’ fisheries.

In the search for new populations of orange roughy to ‘mine’, deep sea trawlers are ever seeking new grounds. Orange roughy tend to congregate on seamounts, which rise above the surrounding seabed at least 1000 metres. These undersea mountains are biodiversity hot spots, and many have unique animals found only on one or a small local group of seamounts. They are smashed to bits by trawl nets with heavy steel rollers on the front to flatten black corals, huge gorgonian fans, bamboo corals and giant sponges hundreds of years old, so that the nets can then get a clear run at the fish once they have nowhere to hide.

Deep sea trawlers regularly fish at 1000 metres and the tops of many seamounts have been devastated. Seamounts on the Louisville Ridge, a spectacular undersea mountain chain east of New Zealand, have been serially trashed by bottom trawling. Other seamounts are picked off one by one, stripping their fish stocks and laying waste the habitat of giant corals and many marine animals totally new to science. Scientists say that bottom trawling is the single biggest threat to deep sea life.

To the credit of the Government, however, the Ministry of Fisheries has protected 19 seamounts from the effects of fishing, but that is out of a total of over 800 seamounts in the New Zealand EEZ. Interesting that the fishing industry is legally challenging the Government over stopping them from fishing this tiny fraction of the seamounts.

In the early days of orange roughy fishing, trawl nets didn’t need to go to the bottom. Vast schools of orange roughy could be fished in mid-water. Some said the stocks were so enormous that they were ‘inexhaustible’. How many times have we heard that before? With advances in technology, combined with the greed for profits, no natural resource is inexhaustible. That has been proved many times by many painful losses.

In July this year the Greenpeace ship Rainbow Warrior documented deep sea trawlers working in international waters in the Tasman Sea. For several days Greenpeace inflatables tracked the ships as they towed their nets and hauled their catch from the northwest edge of the Challenger Plateau. Further east in the New Zealand 200-mile EEZ the fishery had been closed a couple of years ago because it was down to a pitiful 3% of its original biomass, but in international waters there are no controls.

We watched about 15 hauls as they winched the catch up the stern ramps of the trawl vessels. Only one of these hauls was a successful catch of orange roughy, the net coming up with about 10 tonnes of roughy and with very few other species. The Chinese crew put up a cheer when they saw the net, suggesting that a good haul was not a common sight. The other hauls were pathetic, generally around one tonne of a mixture of bottom-dwelling fish species and deep sea urchins and seastars, and the occasional twig of black coral. Most of the hauls we saw contained barely a sugar-sack full of orange roughy. After scraping the seafloor for five hours, this can not be economic. One of the trawler skippers told us that his Company sends them out here after they have caught their quota in New Zealand waters. They go to the high seas in the hope of catching enough fish to pay for the bank loan fees on the fishing boats.

After the net is hauled onboard the crew set to work sorting and processing the catch. The six New Zealand-registered boats would not throw the bycatch overboard while we were watching. But the Chinese vessel was happy to throw over their unwanted fish and orange roughy heads, and we were able to collect some of the wasted species before they either sank or were gobbled up by screaming hoards of albatrosses and petrels numbering in their thousands. A bonanza for the birds, but how is this affecting their behaviour? Instead of scouring over the ocean in search of occasional dead fish, they follow the ships like seagulls squabbling at a rubbish dump.

At a recent United Nations meeting in New York, Greenpeace lobbied for an immediate interim prohibition on bottom trawling on the high seas, to give some breathing space so scientists could find out what is being destroyed by trawling, and work towards a sensible approach to fishing in deep water. The idea was supported by the usual ‘green’ countries, like Costa Rica and Thailand, but opposed by the usual anti-conservatives like Japan and Iceland. A watered-down version was eventually passed, recommending that countries ‘consider a moratorium’ on deep sea trawling on the high seas.

Greenpeace will try again in November at the UN General Assembly meeting.

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