Anglers are being warned to avoid eating fish caught in back country waters as they could be tainted by 1080 poison.
The Department of Conservation plans to aerially drop 1080 poison across 700,000 hectares of conservation land, mostly in the South Island, to reduce rodent numbers.
DOC commissioned independent research into the risk, finding 1080 levels in trout flesh were significantly higher than recognised food safety guidelines.
Fish & Game New Zealand chief executive Bryce Johnson said the results were "not a good look" for New Zealand's so-called 100 per cent pure environmental brand.
“Anglers fishing back country waters, including overseas anglers who come here because of the trout fishery’s international reputation, have always been able to assume that it is totally safe to catch a trout and eat it. Sadly, this turns that over," he said.
DOC's massive 1080 operation had been planned in response to an anticipated "mouse plague" after beech forests produced large crops of seed this year, giving the rodents extra food.
“While we understand why DOC is doing this, the findings from this recent research has added a very significant and concerning new dimension to the 1080 debate”, Johnson said.
He believed the ramifications of the operation would extend "well beyond" the poison sites, but said Fish & Game had "been left with no choice" but to support DOC's warning to anglers.
He called for further research to provide a more accurate picture of the possible risks.
“Fish and Game is not saying don’t go fishing in the back country, just don’t eat the fish," Johnson said.
Department of Conservation boss Lou Sanso played down claims that trout pose a health risk.
''You would have to eat tonnes of trout to be affected,’’ he said.
''Overall the risks are very low.''
The department undertook research at the request of the New Zealand Federation of Freshwater Anglers, Sanson said.
The research involved feeding trout high levels of 1080 in the lab and the preliminary results showed that trout take up small amounts of 1080 into their flesh which breaks down over a number of days.
The results were only laboratory tests, they were not peer reviewed and would need to be replicated in the field to establish their credibility, he said.
The research was done at the Cawthron Institute laboratories, Swanson said.