Feeding habit and intensity of Periophthalmus variabilis caught from some coastal provinces in the Mekong Delta, Vietnam

Dusky-gilled mudskipper Periophthalmus variabilis, a member of the family Gobiidae, is a potential aquarium pet in the Mekong Delta (MD), Vietnam; however, data on its feeding habit and intensity has been limited. Therefore, this study aims to evaluate the relative gut length (RGL) and gastro-somatic index (GI) of Periophthalmus variabilis in order to determine the feeding habit and intensity of this mudskipper and its variation regarding sex, size, season, site, and their interaction. One thousand one hundred seventy mudskipper samples were collected monthly in four locations: Duyen Hai-Tra Vinh, Tran De-Soc Trang, Hoa Binh-Bac Lieu, and Dam Doi-Ca Mau from January 2022 to December 2022. The analysis showed that Periophthalmus variabilis was a carnivorous fish with an average RGL value of 0.52±0.01 SE (<1). In addition, the RGL of this species varied and depended on size, sampling site, season, and the interaction of both size and season with locations. The GI of the mudskipper was 4.27±0.29 SE, indicating that its feeding intensity belonged to the moderate category and varied with size and site but not sex, season, and interactions. These results supplement novel knowledge on its feeding habit and intensity, a basis for researching the aquaculture of Periophthalmus variabilis in MD.