The use of imported pangasius fish in local restaurants

•Pangasius fish often substitute for domestic catfish and grouper in restaurants.•Pangasius was frequently used in restaurant fish dishes without specifying species.•Pangasius fish samples identified in this study were exclusively tra/swai.

Pangasius fish, primarily Pangasius hypophthalmus (tra/swai) and Pangasius bocourti (basa) belonging to the Pangasiidae family of catfish, are an imported farm-raised freshwater fish. The labels “tra/swai” and “basa” seldom appear on restaurant menus, so it is unclear how and to what extent pangasius is used in restaurants. In this study, we investigated 47 different fish products served at 37 restaurants in a city in the southeastern United States. A commercial rapid lateral flow (LF) assay (EZ Pangasius™ kit) was used to identify pangasius fish and the results were verified by enzyme-linked immunosorbent assay (ELISA) using a pangasius-specific monoclonal antibody (mAb) T7E10. Isoelectric focusing (IEF) was then employed to examine the protein patterns in the ready-to-eat fish samples. The results showed that 26.7% of the domestic catfish (Ictaluridae family) and 22.2% of the grouper dishes served were actually pangasius. A high percentage (66.7%) of dishes displayed under the general name of “fish” on the menu were also identified as pangasius, revealing the widespread but economically favorable and/or fraudulent use of this fish in the restaurant industry. The IEF results revealed that the pangasius positive samples were exclusively tra/swai. There was no significant difference in the prices charged to restaurant customers between pangasius negative and positive samples, indicating that price is not a good indicator of fish authenticity. These findings highlight the need for stringent enforcement of the existing regulations to discourage the fraudulent use of pangasius fish, either tra/swai or basa.