Illness traced to waxy fish

Laboratory detective work has helped to identify the real culprit in causing illness from eating fish in southern and eastern Australia.

Oil analysis of suspect fillets by Ben Mooney and colleagues of CSIRO Marine Research found the presumed culprit, rudderfish, innocent of all charges.

“Instead we found that another fish species called escolar was to blame for the ill effects of eating fish in some 200 reported incidents,” Mr Mooney said. “Escolar is a large fish taken as part of the bycatch in east and west coast tuna fishing nets.

“It contains extremely high levels of a wax similar to castor oil which is largely indigestible. Eating a normal serving of 200-gram serve of escolar would be the same as eating two tablespoons of liquid wax.

Mr Mooney said these results show that strict naming of seafood is needed to prevent future incidents.

Mr Mooney’s research was conducted as part of a broader study examining the nutritive value of oils in Australian seafood, funded by the Fisheries Research and Development Corporation.

His investigation into “rudderfish” began after half the guests at an Adelaide function became ill after eating what was believed to be rudderfish.

Sophisticated equipment, similar to that used in testing elite athletes for performance-enhancing drugs was used to do a detailed oil analysis of the fish fillets.

“The oil found in the fillets was different from most of the 200 commercial species of fish in our database,” Mr Mooney said. “We then used oil analysis and DNA fingerprinting on various species of rudderfish and similar escolar species.

“In this way we were able to correctly identify the fish causing the problems.

“In his studies, Mr Mooney also accidentally found that one of the rudderfish species contained exceptionally high amounts of a substance thought to be good for the human immune system.

Mr Mooney announced the results of his research today (23 August) at the 11.15am ScienceNOW! media conference. He will present his research in more detail to the public on Saturday 25 August in the ScienceNOW! session commencing at 10.30am.

Jpeg images are available of the escolar and rudderfish species, as well as Ben working in the Hobart CSIRO marine labs.

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