Climate change may hurt salmon farms

Less rain, warmer sea temperatures, and rising sea levels could hit Marlborough as part of climate change predicted by an international body of scientists.

The report by the Intergovernmental Panel on Climate Change suggests changes to water temperatures and conditions could affect mussel production and potentially stop salmon farming in the Marlborough Sounds.

It says climate shifts potentially suggest "substantial changes in production and profit of both wild fisheries and aquaculture species such as salmon, mussels and oysters. Ecosystem models also project changes to habitat and fisheries production."

Marine Farming Association executive director Graeme Coates said yesterday the report was not a surprise.

The aquaculture industry was concerned about ocean acidification affecting shellfish fecundity, he said.

"On the surface of it, there is not a lot we can do."

Acidification was different to temperature rise, but was a function of global warming, he said. "It's probably far more important to us."

Climate change was difficult, he said, because it was very hard to identify a single causative agent.

"It could be affecting juvenile blue cod. The runoff of soil, change in temperature, acidification, other changes could be affecting things."

Mussels were likely to be less affected. They were grown in the Firth of Thames, near Auckland, which was warmer than the Marlborough Sounds, Coates said.

Salmon were "far more dependent" on water temperature. If sea temperatures in the Marlborough Sounds increased greatly, salmon farming would be much more difficult than it was now, he said, but other finfish could be a more suitable prospect.

"There is probably not much we can do for salmon farming but, as the water temperature increases, other species could be more suitable, such as kingfish or groper."

Coates said the issue was important to the industry, but it was not lobbying the Government on it.

"It could be bloody important but we do not have it on the radar at the moment. We have things that affect people immediately at the moment."

The mussel industry was not a generator of carbon dioxide, he said. In fact, mussel farms were carbon sinks, taking CO 2 to make shells.

The report by the international panel, run under the auspices of the United Nations, had a section focusing on New Zealand and Australia. It said sea-level rises, reduced rain and groundwater changes, and rising sea temperatures would all affect New Zealand, including Marlborough.

It said the northeast of the South Island would get less rain and there would be reduced runoff, which could affect Marlborough's aquifers.

"Climate change will affect groundwater through changes in recharge rates and the relationship between surface waters and aquifers."

Climate change would also degrade water quality, particularly through increased material wash-off after bushfires and floods, the report said.

Sea-level rise was a significant risk for New Zealand and Australia, because of intensifying coastal development and the location of population centres and infrastructure, it said.

"Under a high-emissions scenario, global mean sea level would likely rise by 0.53 to 0.97 m by 2100, relative to 1986-2005, whereas with stringent mitigation, the likely rise by 2100 would be 0.28 to 0.6m.

"Local case studies in New Zealand and national reviews in Australia demonstrate risks to large numbers of residential and commercial assets as well as key services, with widespread damages at the upper end of projected ranges."

The Marlborough Express