Consumers are left even more confused and aggravated when they see that the dory menu served in fine-dining restaurants is charged at more than several hundred baht apiece, while a fish with the similar name is also available in many street diners and can be enjoyed at only 100 baht or so per kilogramme.
But which one is the real dory?
The taxonomic confusion has become an issue when "dory" (or "dolly") has grown into a popular menu in local eateries in the past few months followed by news reports of its possible health hazard _ worms. Ice buckets in supermarkets seem to have more dory on display too, and consumers are not sure of the real identity of the good versus the bad fish.
According to director of the Food and Drug Administration's (FDA) Bureau of Food, Dr Tipvon Parinyasiri, the controversy regarding these different dory versions available on the market involves only two different fish families _ zeidae and pangasiidae.
"The famous and pricey John Dory is an edible marine fish in the zeidae family," explained Dr Tipvon. "This white-fleshed sea fish can be found in European deep waters and is consequently very expensive."
But another so-called dory fish commonly available in many hotpot franchises, as well as street diners, is apparently not John Dory which is, added Dr Tipvon, sold at 300 to 400 baht a piece.
"What is claimed to be dory fish is in fact a species of freshwater fish in the pangasiidae family," the director said. "This kind of fish is much smaller in size than the John Dory and the price is much cheaper, too."
People in different countries have different names for this type of fish. In Thailand, it is usually known as pla sawai. In Laos, it is referred to as pa sooai while in Vietnam, people call it ca tra. In some areas, it is named basa.
Dory is a generic name that people unofficially give it and this has led to confusion and misunderstanding among consumers and restaurant operators alike.
To fix all the fuss about these two different fish families, the FDA has joined with the Department of Fisheries and asked for collaboration from fish manufacturers and importers to clarify product labels. Fish that falls into the pangasiidae family is to be labelled "pangasius dory".
"The FDA has asked fish importers and manufacturers to add the word 'pangasius' to the label given it is the scientific name of the fish," noted Dr Tipvon. "Therefore, from now on, if the product is tagged 'pangasius dory', it suggests the freshwater fish and apparently not the John Dory."
Dr Tipvon added that the majority of pangasius dory available in the Thai markets is raised and imported from Vietnam as the country has been developing itself to become one of the world's largest pangasius dory fish exporters. And as a result, pangasius dory is sometimes referred to as Vietnamese sawai.
Last year alone, Vietnam produced 1.2 million tonnes of Vietnamese sawai, half of which was for export and worth 54 billion baht. Vietnam exports sawai to 135 countries around the world, with the US and the European Union its largest market, accounting for 47% of the country's sawai export value.
While pangasius dory has become quite popular among consumers and street diners due to its good flavour, yet low price, at the same time the imported fish is claimed to be fed with animal carcasses and to have worms, causing adverse effects on consumers' health.
The director of the Bureau of Food said that while it is possible domesticated fish may be fed with animal meat or even animal waste, when it comes to fish farming _ especially on a very large scale such as for export _ it is less likely that farm operators would jeopardise their own businesses by giving dead animal bodies to the fish, which could potentially lead to deadly contamination.
''Take how some Thais keep and feed pla duk [catfish], for example,'' said Dr Tipvon. ''In many places, the fish pond is placed underneath chicken cages so that the fish is fed with chicken faeces. But for large-scale fish farms, normally farm operators will feed the fish with fish food. Giving dead animals to fish might put the business at risk of losing all the fish in the farm because [even] if only one fish gets infected, it affects all others.''
And if consumers are concerned about worms found in pangasius dory, it is about time they understand one simple truth _ all freshwater food products can have worms.
Freshwater fish, freshwater mussels or even freshwater algae should not be eaten raw, Dr Tipvon recommended. So, for safety reasons, freshwater products _ especially fish _ must be cooked at the minimum temperature of 100C. At this temperature, worms will be killed and food will be safe to eat.
''Worms and contaminated seafood can potentially cause food poisoning as well as other digestive diseases,'' said the Bureau of Food's director. ''Therefore, especially when you opt for jim-joom [Thai-style hotpot], it is crucial that you leave the fish, as well as other types of meat in boiled water long enough to ensure they are thoroughly cooked. This way, you can protect yourself from illness.''
When it comes to buying goods from supermarket, Dr Tipvon said that it is strongly advisable for consumers to read the product labels carefully. This is one easy way they can make sure they spend their money on the right commodity.
''The John Dory and pangasius dory can be differentiated not just by price, but also by how they look,'' Dr Tipvon commented. ''The expensive John Dory will usually come as a thick piece, while pangasius dory is sold in thin slices. But the easiest way for consumers to make sure they do not go for the wrong type of fish is to read the label carefully.
''The FDA has enforced a strict labelling control among fish importers with punishment regulations. So if consumers read product labels carefully, it is one effective way to shield themselves against any mistakes that might occur.''