Where are we and what do we know? A recent study by the Department of Conservation and the Marlborough District Council found 129 ecologically significant marine sites in the Marlborough Sounds. Many of them are already degraded. The same report advised a reduction in the amounts of contaminants reaching the marine environment.

The Marlborough regional policy statement does not promote the free release of waste in our waterways, such as from concentrated finfish farming.

King Salmon has only surveyed bottom substrates which amounts to 15 per cent of the waste, not the wider environmental impacts in which the other 85 per cent of their waste is released.

In 2009, the highest level of organic pollution at any of the NZKS farms was recorded under the Waihinau operation in the Pelorus Sound (Cawthron report 1740). Also zinc and copper were at levels above or near the highest set criteria (Cawthron report).

King Salmon does not monitor the release of nitrogen in the Marlborough Sounds. Increases of nitrogen can create a shift in plankton communities and plankton biomass. This process can push the environment in a cycle of harmful algal blooms miles from the farm site.

We do not know how much King Salmon has already pushed the functionality of the environment in this direction because King Salmon has never ordered a report to be done.

The impact of the King Salmon application is only proposed as a model, a model that has been developed in Norway and never been tested in New Zealand. We ask why has New Zealand King Salmon not ordered their science provider to test the overseas model with their existing farms? Models that predict environmental impacts, no matter how good, have no credibility unless they are supported by empirical evidence.

Sustain Our Sounds Inc maintains that no studies have been done in the Marlborough Sounds on the impact of nitrogen release by concentrated finfish farming.

Excessive nitrogen is a contaminant. The proposal of King Salmon will seek approval to release nitrogen from the waste of the equivalent of half a million people into the Marlborough Sounds. These figures have been acknowledged by both King Salmon and Cawthron with our science provider.

Eutrophication, (excessive nitrogen) is the leading cause of water quality impairment around the world. Harmful algal blooms can cause kills of all living marine resources and shellfish poisoning, which is also harmful to humans.

We say the risk is far too great. We say without the science, a precautionary approach needs to be taken.

New Zealand King Salmon chief executive Grant Rosewarne responds:

There are many factors affecting the marine environment in the Marlborough Sounds. Well-documented salmon farming research demonstrates there is no evidence our operations have damaged the 129 sites to which Mr Boulton refers.

Our footprint is small, localised and managed to its maximum assimilative capacity in balance with the environment. Regular independent testing ensures the extent of our impact is known and there are no identifiable remote effects in the wider Sounds that Sustain Our Sounds or anybody else has been able to credibly demonstrate.

Native worms and micro-organisms underneath our farms break down the organic matter that reaches the sea floor. Both copper and zinc are micronutrients required for life. Zinc is important to stop fish developing cataracts. We now use organic zinc in our feed because it is more easily ingested, which has halved our use.

We have many different types of nets but use copper only on our predator nets and keep it to a minimum. Many people will be using a similar type of antifouling on their vessels.

We regularly test for nitrogen in the water column and cannot detect any difference a very short distance from the farms. Sustain Our Sounds has to accept the scientific evidence that clearly shows the amount of nitrogen coming from a salmon farm is small compared to that entering naturally from Cook Strait.

Testing over the wider environment is a function for government but we would be happy to redirect some of our monitoring efforts towards this because we believe this will further reinforce our track record.

Any doubts about nitrogen enrichment should have been well and truly vanquished by Dr Rob Murdoch's comments reported in this newspaper. He said the predominant drivers of change (in nitrogen levels) were what was happening in the open ocean and from river flows.

From a practical point of view, Marlborough Sounds residents are well aware that mussels, which feed on phytoplankton based on nitrogen, are growing more slowly which is an indication of nutrient deficiency, not excess.

We have excellent data from the real-life example of our 8000-tonne production as well as a model based on 1 million tonnes of actual Norwegian production.

It's disappointing that Sustain Our Sounds continues to ignore that for 25 years we have been farming in the Sounds in balance with the environment.

Our existing practices are supported by the wider Marlborough community. The overwhelming weight of scientific evidence indicates little risk but huge economic gains for the region from our plans.

- The Marlborough Express

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