Increasing intensity of fish production in many regions, extensive inter-regional transport of fries, fingerlings and fishes, and the adverse effects of antibiotics and other chemicals, call for the intense research" on the prevention of fish diseases. In the context of unavailability of efficacious and affordable vaccines for number of fish diseases, a relatively new and promising area of research is immunostimulants for increasing the disease resistance of fish. An Immunostimulant by definition is a drug or chemical that elevates the nonspecific immune mechanisms and specific immune responses (the latter, if the treatment is followed by infection or vaccination). The present invention is the development of an efficacious immunostimulant from a marine plant which can be used as an immunoprophylactic for culture fishes. An immunostimulant is an effective alternative to antibiotics and even the fish vaccines. Fish vaccines may be very expensive to the fish farmers because of the number of vaccines needed and also the cost of labour-intensive vaccination process. Immunostimulant when used as a therapeutic, can also effectively replace the adverse antibiotics which not only pollutes the environment but also leads to the development of resistant bacterial strains. The present invention was made by extracting the marine macroalga (seaweed) (CFI-MA 04) (selected after screening the crude extracts of many species of macrolagae for disease resistance on experimental challenge with a virulent bacterial pathogen) with alcohol and separating various classes of compounds from the alcohol extract using internationally accepted biochemical separation methods followed by testing the various fractions for immunstimulatory and disease protecting (resistance) properties and selecting the fraction which exhibits maximum immunostimulatory and disease resistance properties as the candidate immunostimulant product. ■The product invented is very efficacious and is intended to be used as a
