Wild larvae in three different river mouths: Location 1: Thuan An river mouth, Thua Thien Hue province, Vietnam (13°45'42.4"N 109°14'45.5"E). Location 2: Cua Dai rivermouth, Quang Nam province, Vietnam (15°52'38.1"N 108°24'00.2"E). Location 3: Thi Nai river mouth, Binh Dinh province, Vietnam (16°34'46.0"N 107°37'17.5"E) were collected on 8th - 10th of June when the wild fish first occur in the river mouths for over three-year period (2014, 2015 and 2016) (figure 1). Larvae of each sampling point were collected by fishing net in the early morning between 7AM and 8AM. The larvae was first washed with the distilled seawater, after that the larvae were kept on ice and transported to the laboratory, where they were freeze-dried. The freeze-dried samples were preserved at -20° C for the analysis of Fatty Acid Methyl Ester (FAME) composition and gut microbiota.