Shark catfish for instance is exported to around 140 countries, including the US and the EU, and shipments this year are expected to be worth over US$2 billion, but is not popular in Viet Nam.

Speaking at a panel discussion on developing the domestic market for shark catfish last month Dr Ly Thi Thanh Loan, member of the executive committee of the Viet Nam Pangasius Association, said distribution and market segmentation have not been done well.

Nguyen Van Dao, general director of Go Dang Seafood Company, said shark catfish companies mostly focus on export rather than selling to Vietnamese consumers.

The Viet Nam Association of Seafood Exporters and Producers has been pushing to ease restrictions on traces of prohibited chemicals and antibiotics in seafood before Tet (Lunar New Year) holidays, which comes around early next year.

This year some supermarkets have been refusing to accept seafood containing cloramphenicol, an antibiotic that is prohibited in seafood, though its content was under 0.3 ppb (parts per billion), low enough for acceptance in the EU.

The companies selling the seafood said Vietnamese regulation are too stringent, claiming traces of the chemical would not harm consumers.

The Ministry of Agriculture and Rural Development said this is a relatively new problem which requires authorities to investigate further.

Its Agro Processing and Market Development Authority also said some seafood firms are struggling to sell domestically due to cumbersome procedures.

Last year 31 kilogrammes of seafood were consumed per person in Viet Nam, which could grow to 33-35kg by 2020, Nguyen Quoc Toan, deputy head of the authority, added.