Efficacy of organic acids on survival of milk fish (Chanos chanos) larvae as a bath treatment

Abstract

The disease outbreak in the aquaculture industry, coupled with ban on antibiotic usage due to residues in animal tissues and spreading of antimicrobial resistance ignites to find an alternative approach for control of bacterial infections in aquaculture, especially in the larval stages of fishes. Use of organic acids holds a promising substitute to antibiotics. To study the efficacy of organic acids, a bath treatment experiment was carried out in 12 L plastic tubs to find the effective concentration at which no mortality of larvae treated with different organic acids viz.,acetic acid, lactic acid, malic acid, formic acid and citric acid concentrations for 10, 15, 30 and 60 minutes respectively. The milk fish larvae were treated with six concentrations(In percentage) viz., 1, 0.2, 0.1, 0.075, 0.05, 0.025, with all the organic acids for different time intervals and later complete water was exchanged. The study was conducted separately for all organic acids at six different concentrations. Survival rates of the fish larvae were noted at the end of each acid treatment for respective time period and after 24 hours. Total mortality was observed at 1, 0.2, and 0.1 per cent for all organic acids for all time intervals. Results revealed that the effective concentrations at which no mortality observed were 0.05, 0.075, 0.05, 0.025 and 0.075 per cent for acetic acid, lactic acid, malic acid, formic acid and citric acid, respectively. From this study, it can be deduced that, the above organic acid concentrations may be used for treating the fish larvae at which no mortality observed, as a safe concentration. Further, these concentrations may enhance immune response and reduce the pathogenic microbial load (Vibrio spp.) from the larvae which cause mortality in stressed conditions.