A one-year study was conducted to assess the population of Butis koilomatodon, a target fish for food supply, based on a total of 1227 specimens (891 males and 336 females). The sample were collected from Tra Vinh to Ca Mau provinces, Mekong Delta, Vietnam. The ELEFAN I procedure and the model of Beverton & Holt about yield-per-recruit were used to analyze the fish population's biological parameters. Data analysis results showed that males outnumbered females in the population structure, with a sex ratio of 2.65:1. There were 4 classes of length frequency, with the highest values between 5-6 cm and 9-10 cm (accounting for 1204 fish, 98.13% out of the total number of samples). The von Bertalanffy curve of the goby showed a total length (Lt) value of 9.99 (1-^{e-0.94(t+0.3)}). The value of the longevity was 3.19 years, and the index of growth performance was 1.97. The total, natural, and fishing mortalities of the fish population were 2.91 year-1, 2.37 year-1, and 0.542 year-1, respectively. The indices of relative yield and biomass of B. koilomatodon recruits were Emax=0.421, E0.1=0.355, and E0.5=0.278. As the exploitation rate (E=0.19) was lower than E0.5, the fish stock was not overexploited. Overall, the fish stock has the potential for exploitation, and this mud sleeper goby could be a potential candidate for artificial aquaculture due to the high growth coefficient.