Increased survival rate of hybrid grouper Epinephelus sp. after feeding with microalginate particles

Abstract

This research aims to increase fish survival rate by providing oral feed containing formalin killed cells of Vibrio alginolyticus. It investigates whether it is effective or not. In the hatchery, the survival rate of grouper Epinephelus sp. is only 2-3 percent. The death of 4-6 g size grouper infected byVibrio sp. is very quick. Fish dies only after 12 h of infection. The problem on larval stage is that the fish size is small. So, it is not possible to perform injection or immersion because it may result in high stress of the fish. The only way to overcome the problem is oral provision by incorporation of feed. Formalin-killed cells of Vibrio were coated with alginate and administered orally through feed. Alginate microparticles were prepared from colloidal complexes using sodium alginate gel as a core. All alginate solutions (2% w/v) were prepared by dissolving sodium alginate in deionized water. The survival rate of fish increased to 20–22 percent; the antibody titer was 64-256 and phagocytic rate was 32-60. The increased survival rate was due to higher antibody and superoxide production in fish. This study suggests that vaccination for small fish can be done in the future by making various improvements.