Two Canterbury high-country lakes have been closed to trout fishing because of a possible fish disease.
The Ministry for Primary Industries is checking whether an exotic disease has infected rainbow trout.
Rashes have been spotted on a small number of the trout in Lake Grasmere and the ministry has closed it to fishing as it carries out tests.
Nearby Lake Sarah has also been closed as a precaution.
The ministry expects test to establish whether the fish are carrying disease to take at least three weeks.
A spokesperson said the possible fish diseases in question did not pose a risk to those who eat them.
Fish and Game chief executive Martin Taylor said the risk was handled well.
“It was really good the system worked well. An angler saw there was an issue, sent pictures and fish were caught with the same markings. We then worked with MPI and DOC to make sure everything was handled quickly,” he said.
Mr Taylor said the last biosecurity risk he has on record was the didymo algae outbreak, but a disease directly impacting fish was unheard of.
The ministry reminded anglers of the importance of cleaning their gear when fishing different waterways.