THE EFFECT OF IMMERSION OF MANGROVE Avicennia alba (Tomlinson, 1986) LEAF EXTRACT WITH DIFFERENT CONCENTRATIONS IN PREVENTING BACTERIAL DISEASE Vibrio harveyi (Johnson & Shunk, 1936) IN VANAME SHRIMP (Litopenaeus vannamei) (Boone, 1931)

Vibriosis is a disease that often attack shrimp culture , some of the most dangerous types of Vibrio bacteria are V . harveyi . The use of natural materials is an alternative that can be applied to prevent bacterial disease . One of the mangrove species that has an antibacterial compound is A . alba . A . alba ha s alkaloid, saponins, and flavonoids compounds that can inhibit the function of cytoplasmic membranes and energy metabolism in bacteria. T his study was conducted to determine the effectiveness of A . alba leaf extract A . alba in inhibiting V . harveyi disease in vaname shrimp ( Litopenaeus vannamei ). This research was conducted in several stages, namely extraction of mangrove leaves, both in vivo and in vitro . The highest SR, RPS and MTD values were obtamed at a concentration of 250 mg/l with each value of 80 %, 60 %, 75 th respectively hour. M angrove leaf extract A . alba was able to prevent diseases caused by the bacteria V . harveyi , with the best results at an extract concentration of 250 mg/l where the concentration can significantly higher SR, RPS, and MTD compared to other treatments.