Poisons used for pest control in Southland are being found in fish in waterways in the region.
Anticoagulants found in the likes of rat poison have been discovered in the livers of eight freshwater fish after routine inspections.
Southland Regional Council said the discovery is concerning but not alarming.
Aquatic ecologist Andy Hicks said it's most likely that a poisoned animal has died near water and been eaten by fish.
The anticoagulants have not been found in the fish flesh, which is eaten by people.
Dr Hicks said the regional council is seeking guidance from Government agencies on how to manage the situation.