Fishing over summer? Watch out for ‘zombie snapper’, Fisheries NZ warns

Anyone putting out a rod over summer should look out for cloudy-eyed snapper, warns Fisheries NZ. Photo / NZME

Summer might be a great time to hit the water and drop a line, but Fisheries New Zealand is warning fishers to look out for and report any “zombie” fish.

The term zombie fish was first coined by Kaipara Harbour recreational fisher Sam Erickson in May, who caught snapper so sick he thought they were “like the walking dead”.

Symptoms include cloudy, cataract eyes, sunken face, a lack of mucus and lack of flesh.

The Ministry for Primary Industries’ Fisheries New Zealand received samples of sick snapper from around the North Island, including Kaipara Harbour’s Northland and Auckland territories, Whangārei Harbour, Raglan and Paekākāriki Harbour.

Tests were done but a cause for the sickness has not yet been found.

Fisheries NZ has now launched a new webpage calling the fish “cloudy eyed snapper” and is asking fishers to provide samples of snapper or any other fish with the symptoms.

Fisheries NZ director science and information Simon Lawrence said affected fish will continue to be tested over the 2024–25 summer as a precaution.

“Anecdotally, there have been fewer reports of fish being caught with this condition recently, which may indicate seasonal factors at play.

“While the cause is still unknown, we’ll continue to monitor and test samples over the summer months, particularly when biotoxins are likely to be more common,” he said.

The 12 samples tested were caught in May, June and July, so samples caught over summer may provide more clues as to the cause.

Fish samples are best sent to the Biosecurity NZ’s animal health laboratory within 24 hours, so Lawrence encouraged fishers to photograph affected fish, keep them whole and chilled and phone Fisheries NZ on 0800-809-966 as soon as possible to arrange collection.

The diseased "zombie" snapper, right, have sunken, milky eyes, bones sticking out and a lack of mucus on their skin.

He warned against eating the sick fish.

“While we have not found any food safety concerns, our advice is that if any animal you catch or hunt looks unhealthy, including snapper showing the cloudy eye symptoms, you should not eat it.”

If anyone eats the sick fish and becomes sick themselves, they are advised to go to their GP in the first instance.

Cause of fish sickness still unknown

Lawrence said tests of the cloudy-eyed snapper to date has not confirmed the cause, although the pathology was found to be different to fish with milky white flesh syndrome, which impacted snapper in the Hauraki Gulf and east Northland. That was found to be linked to starvation or a lack of food.

Initial analysis by Biosecurity NZ’s animal health laboratory could not find any biosecurity concern over exotic diseases, parasites or infectious agents in any of the fish.

A report from Biosecurity said an environmental pollutant was the most likely cause and it recommended more testing.

“While we cannot categorically rule out an unidentified infectious agent at this stage, it is most likely that an environmental pollutant, chemical, heavy metal or toxin is causing the changes observed,” the report said.

Voluntary samples of Kaipara Harbour’s Northern Wairoa River found alarmingly high levels of aluminium, more than 30 times the freshwater standards.

In June, samples were tested by Cawthron Institute for pollutants that might be causing the symptoms such as heavy metals, including aluminium and lead, as well as a wide range of PCB chemicals.

But Lawrence said levels of all heavy metals and chemicals were found to be within normal ranges.

In September, Cawthron Institute screened the livers of the affected fish for naturally occurring biotoxins. They were analysed for 70 marine and freshwater toxins but none were detected in the livers.

Comments from the laboratory test reports show consistency in symptoms between the fish caught on the west coast of the North Island and Whangārei on the east coast, including cataracts, liver damage and some kidney damage.

The reports said the main concern was heavy metals or environmental pollutants or chemicals, although consideration should still be given to an unknown virus, marine biotoxins and bacterial produced toxins or unidentified bacterial agents.

What to do if you catch a zombie snapper?

Lawrence said anyone wanting to provide fish samples to Fishiers NZ should:

• call 0800-809-966 as soon as possible
• keep the fish whole (not gutted or filleted)
• store the fish in the fridge (not the freezer).

Denise Piper is a news reporter for the Northern Advocate, focusing on health and business. She has more than 20 years in journalism and is passionate about covering stories that make a difference.