It is not possible to detect the toxin before eating the fish, which appear quite healthy and the taste and smell of the flesh is not affected.
Probably the simplest precaution is not to eat the fish if your hands feel numb after cleaning
it, or if there is any suggestion of a stinging sensation after skinning or filleting it.
Some authorities recommend feeding the viscera of the fish to a cat and confine it for observation. However, the cat may vomit, become uncoordinated, or even die within 48 hours. This is obviously extremely hard on the poor cat, and a more humane option should be entertained first. Testing a small amount of fish flesh on a healthy adult in your party the night before is a better solution, if you can find a willing victim.
A few other avoidance measures include:
Ask the locals as the toxic fish may be confined to a narrow area like one side of a small island.
Avoid the biggest fish of the catch.
At no time eat or handle red bass, chinaman fish, paddle tail, or moray eels.
If still in doubt, stick to safe fish like mullet, whiting, bream and flathead.
The poison is very stable and resistant to heat and drying, so cooking
does not deactivate the poison. Soaking the fish won't work
either as the poison is not water
source: Ciguatera Poisoning AndFishing On The Great Barrier Reef