The "zombie" snapper are being tested at the Ministry for Primary Industries' national animal health laboratory in Upper Hutt, for any exotic or emerging diseases.
The "zombie" snapper are being tested at the Ministry for Primary Industries' national animal health laboratory in Upper Hutt, for any exotic or emerging diseases.
Symptoms of the illness in the snapper include milky eyes, a sunken face, missing flesh, a missing mucus layer and lethargy when caught.
Fisheries NZ, a division of the Ministry for Primary Industries, has received 11 reports of snapper with similar symptoms, science and information director Simon Lawrence said.
Dargaville recreational fisherman Sam Erickson first noticed sick snapper near Ruawai, in Kaipara Harbour’s Northern Wairoa River, in April and coined the term “zombies” because they looked like the living dead.
The fish appear to have symptoms different to fish with milky white flesh caught on Northland’s east coast and Auckland’s Hauraki Gulf in previous years.
Recreational fisherwoman Steph Treadwell also caught two “zombie snapper” in early June in Kaipara Harbour’s Ōruawharo River, west of Auckland’s Wellsford.
The reports have come mostly from the Northland and upper North Island area, with a small number from elsewhere in the island, Lawrence said.
No fish species other than snapper have been reported to have the symptoms.
From these reports, five snapper have been collected for testing by Biosecurity New Zealand at the ministry’s animal health laboratory, he said.
“This testing aims to rule out exotic or emerging diseases and may help us gain an understanding of the cause of the symptoms.”
Early results from one snapper do not indicate any biosecurity concern over exotic diseases or infectious agents, so far, Lawrence said.
Cataracts and inflammation were observed in both the snapper’s eyes. Cataracts in fish were long documented and had many causes, he said.
The diseased "zombie" snapper have sunken, milky eyes, bones sticking out and a lack of mucus on their skin.
Scientific studies show cataracts can be caused by artificial toxins, low temperatures, nutritional deficiencies, parasites in the blood, radiation damage, and trauma from careless handling. They can be a signal of serious nutritional problems.
Studies show cataracts in fish can be associated with an inability to feed and can ultimately cause death.
Lawrence said the snapper also displayed some internal scarring or thickening of tissue, where the cause is unknown.
Bacteriological testing is continuing for this fish, while the four other samples are also undergoing the full range of testing.
Food Safety NZ is also conducting separate tests to rule out any food safety issues with fish displaying the symptoms, he said.
While there are no results available from this testing so far, its advice is to not eat any fish caught if it looks unhealthy.
Lawrence said anyone who catches fish with these symptoms, or who is concerned about the state of any fish they have caught, to report to to Fisheries NZ on 0800 80 99 66.
Any fish for reporting should be photographed and kept whole and chilled, rather than frozen.
Lawrence urges fishers to contact Fisheries NZ as soon as possible, as samples are best when they can be sent to the lab for testing within 24 hours.
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.
