Poison warning on fish species

Food safety and health officials say fishermen and consumers need to be more aware of the potential for dark-skinned fish - such as kahawai, mackerel, tuna, bonito and kingfish - to trigger scombroid poisoning in humans.

The Food Safety Authority has called for recreational anglers and commercial fishers to chill such fish to less than 7C within four hours of death, and to continue to lower the temperature after that.

When the fish are killed, bacteria in the flesh begins to convert the amino acid histidine into histamine toxins, which are not destroyed by cooking or freezing.

Symptoms of histamine or scombroid poisoning usually occur within four hours of eating the fish and include tingling or burning sensations in the mouth, a rash, headache, hives or itchy skin, nausea, vomiting and diarrhoea. Symptoms can last for several days but usually disappear within 12 hours.

The authority said in its magazine, Food Focus, published this week, that sometimes lower-value fish such as kahawai were more likely to be left until last to be put on ice or chilled.

"Sort scombroid species first, to allow faster cooling, before turning your attention to the rest of the catch," the authority said.

But the creation of toxins could occur at any stage between getting the fish from the ocean to the table - wholesalers and retailers needed to make sure scombroid fish were kept at temperatures below 4C, and consumers needed to minimise the time the fish was at room temperature.

Other health officials have said affected fish could have a "peppery" or bitter taste, but usually it was impossible to tell from the look or smell of a fish if it was contaminated.

In May 2003, the authority warned people not to eat smoked kahawai bought from several North Island supermarkets and two fish retailers after they were linked to suspected cases of scombroid histamine food poisoning.

And the Auckland District Health Board said in its latest public health newsletter that a further four fish markets were implicated in cases of scombroid poisoning between June 2003 and July last year.

- NZPA