The Department of Conservation is warning anglers not to eat trout in areas where 1080 poison has been dropped - a reversal of its position seven months ago.
The caution comes just days before the trout fishing season opens on October 1.
Preliminary results of a DoC-commissioned study by the Cawthron Research Institute has shown the flesh of trout that ate mice containing the toxin would have levels of 1080 that exceeded New Zealand Food Safety Authority limits.
The warning is in contrast to the department's rejection, in February this year, of claims by the Federation of Freshwater Anglers that people should not eat trout because of a risk the poison could be present in the flesh of trout and eels.
Yesterday, DoC advised anglers to take a "zero risk" approach and not eat fish from catchments where 1080 had been dropped.
But the department said the risk to human health was extremely low.
"Researchers calculated that at these levels, an 80kg adult would need to eat more than 14 tonnes of trout flesh in one serving to have a 50 per cent chance of receiving a fatal dose."
Bryce Johnson of Fish and Game said he thought DoC had played down the issue in its statement.
"They commissioned the research. If they're saying take a zero-risk approach, and in the next breath saying you've got to eat 14 tonnes of trout flesh, it makes a mockery of their own advice."
David Haynes of the New Zealand Federation of Freshwater Anglers said research showed trout that had eaten a single poisoned mouse could contain more than 40 times the Food Safety Authority Limits.