Anabas testudineus is one of freshwater fish living in the peat swamp area in the Pelalawan Village. A study aims to determine the reproductive biological aspect of betok fish. The fish was sampled 6 times, from March to May 2019. Parameters measured were sexuality, sex ratio, gonad maturity level, gonad somatic index (GSI), fecundity and egg diameter. Result shown that there was 102 fishes, 60…