Gambierdiscus Toxins Increasing by 60%

Incidences ofCiguatera Fish Poisoning Nearly Three Times Higher Than Last Year

Heidi Hollis was working at an RSL Club in Evans Head on the northern NSW coast back in February when she and several colleagues tucked into a lunch of Spanish mackerel.

What followed was months of pain as food poisoning-like symptoms initially sent her to hospital for several days and left her with persistent nerve damage.

"I was unable to walk until a week ago," Ms Hollis said.

The source of the ailment, though, was much worse than a standard dodgy meal. Rather it was triggered by toxins contained in certain fish that are difficult to detect and can't be destroyed by the cooking.

Known as ciguatera fish poisoning, the illness has been mostly tropical. Early Pacific explorers described it as far back as 1606 and even in 1776, during the second voyage of James Cook. More than 1500 cases have been documented in Australia since 1965 and the number appears to be rising.

The toxins are produced by marine microalgae, particularly the gambierdiscus genus. As fish graze on the algae and are then eaten by other fish, toxins accumulate up the food chain to levels harmful to humans.

This year, NSW had its first cases of the illness from fish caught in the state's waters, with Food Authority NSW documenting four at Evans Head -including Ms Hollis -and Scotts Head, also in the state's north.

Researchers, including Shauna Murray from the University of Technology, Sydney, have also detected gambierdiscus as far south as Merimbula for the first time.

"We never realised until now that they could survive in such cold conditions," Dr Murray said.

She said it's difficult to tell for certain whether the Merimbula microalgae - which don't contain the ciguatoxin - had been there all along or was a recent arrival. What is known, however, is that the East Australian Current is strengthening because of global warming, bringing warmer water and sub-tropical species into previously more temperate seas.

These include Spanish mackerel, the species of fish that led to the poisoning in NSW and most if not all of the 55 cases in Queensland so far this year - almost triple the tally of last year.

Dr Murray says the Sydney Fish Market is among the most active markets in Australia in imposing limits on the sale of certain fish to reduce the likelihood of poisoning. Since 1999, it has barred the sale of Spanish mackerel larger than 10 kilograms whole, or 8 kilograms gutted - limits often not known to many recreational fishers.

Food Authority NSW says other species that have caused ciguatera poisoning in humans include coral trout, red emperor, wrasse, reef cod, sturgeon fish, trevally, queenfish, chinaman, red bass, groper, barracouta and kingfish.

"The higher risk tends to be the predatory species that eat herbivorous fish," said Christopher Bolsh, senior lecturer at the University of Tasmania's Institute for Marine & Antarctic Studies. "Ciguatera is probably the most serious human seafood poisoning issue."

Source: SMH

Read More Related Content On This Topic - Click Here

Media

Taxonomy

• Public Health
• Pollution