VNU Journal of Science: Natural Sciences and Technology, Vol 34, No (2018) 16-20 The Relative Gut Length and Gastro-somaticindexes of the Mudskipper Periophthalmodon septemradiatus (Hamilton, 1822) from the HauRiver Dinh Minh Quang1,*, Tran Thanh Lam2,3, Nguyen Thi Kieu Tien4 School of Education, Can Tho University Dat Lat University; Bac Lieu University Centre for Continuing Education of Soc Trang, An Khanh High School, Can Tho Received 17 August 2018 Revised 04 September 2018; Accepted 06 September 2018 Abstract: This study provided an understanding of feeding habit and intensity of the mudskipper Periophthalmodon septemradiatus, which was a potential aquarium pet, by analyzing the relative gut length (RGL) andgastro-somatic (GaSI) indexes Fish specimens were caught by fishing rods from the estuary in Soc Trang province to the upstream in An Giang province of Hau River during a period of one year from August 2017 to July 2018 Data analysis of a collection of 1,504 fishes showed that RGL did not change with fish size, resulting in the feeding habit of P septemradiatus did not change with fish size By contrast, the feeding habit of this mudskipper varied with place, month and season as the RGL significantly different between place, month and season, but both males and females fall into carnivorous fish as RGL was