The purpose of this study was to investigate antibacterial activity of seagrass Cymodocea serrulata. The 6th acetone fraction from C. serrulata root extract showed maximum activity [12mm, 12mm and 12mm] against three [A. hydrophila, B.subtilis and Serratia sp.,] of the five fish pathogens tested and minimum activity of 7mm, 8mm was noticed against V. parahaemolyticus, V.harveyii respectively. The 1st fraction of hexane from C. serrulata root extract showed antibacterial activity against five fish pathogens viz., B. subtilis, A. hydrophila, V. parahaemolyticus, Serratia sp., and V. harveyii. This showed maximum activity [10mm] against V. parahaemolyticus and minimum activity of 8mm, 7mm were observed against B. subtilis, Serratia sp., respectively.
