Both seabed mining companies that have had applications to mine in New Zealand's Exclusive Economic Zone say they intend to keep their projects alive.

Chatham Rock Phosphate, whose application to dredge phosphate nodules off the Chatham Rise, 400 kilometres east of Christchurch was turned down yesterday by an Environmental Protection Authority decision-making committee, is mulling whether to appeal the decision or to mount a fresh appplication.

TransTasman Resources, whose proposal to dredge ironsands from the ocean floor in the southern Taranak Bight was turned down last June, also issued a fresh statement after the CRP decision, saying it "believes that a marine consent for offshore mining within the EEZ can be approved and is proceeding to reapply for a marine consent.

CRP's managing director, Chris Castle, told Radio New Zealand the company was investigating the potential to undertake a wider study of the stony corals in the mining area which the EPA committee found to be "potentially unique".

Describing the committee as having "an absurd preoccupation with stony corals that occur all over the EEZ", Castle said it was only because CRP had conducted some of the most extensive research available on stony corals that the EPA decision-makers had become concerned about them.

"It's not a unique environment just there. Ridiculously, because we've put an area under the microscope it's suddenly become unique because it's the only bit that's really well understood. So what we will do, for example, seeing there's such a preoccupation with stony coral, is to demonstrate these are prolific around the rest of the EEZ and our particular area's not unique."

An EPA official briefing media at the consent decision announcement yesterday confirmed knowledge about the spread of stony corals was incomplete.

"Not much is known about the corals," said the EPA's general manager for applications and assessment, Sarah Gardner. "It would be fair to say there's not as much detail to make a good assessment of whether they are present anywhere else. There was far more information available in the 820 square kilometre area than in the broader 5,000 square kilometre area" and no information on whether bottom-trawling by the fishing industry was destroying such corals elsewhere.

The decision-making committee largely discounted claims by the fishing industry that the CRP project could adversely affect spawning grounds, although it did give weight to the fact that the Chatham Rise is part of a benthic protection zone, which makes it off-limits to bottom-trawling, which scours the seabed and creates damage. CRP's inability to sufficiently mitigate, remediate or avoid damage to the seabed was one of the reasons the mining application was rejected.

Castle described the decision as a "setback", but insisted "we're not dead".

Environmental groups hailed the decision, with Kiwis Against Seabed Mining calling for a moratorium on seabed mining projects.

The Royal New Zealand Forest and Bird Society said the EPA had got it right.

"We are very pleased with the EPA's decision. This was radical new technology, which had never been tried anywhere else in the world and the risks were too great," advocacy manager, Kevin Hackwell, said.

Straterra, the mining lobby group, said the decision showed the new regime governing economic activity in the EEZ, which extends out to 200 kilometres from the New Zealand coastline and is the fourth largest such area in the world, needed fixing.

"The intent of the Exclusive Economic Zone and Continental Shelf (Environmental Effects) Act is to provide for responsible economic development in the EEZ," said Straterra executive director Chris Baker. "However, the Act's requirements for information and consideration of uncertainty mean that any mining proposal would likely be declined.

"What mining investor is going to be brave enough to test that in the future?"