Role of Water Quality on Incidences of Motile Aeromonas Septicaemia (MAS) in the Carp Culture System of Assam

Influence of water quality on the incidence of bacterial disease i.e. Motile Aeromonas Septicaemia (MAS) in the Indian Major and minor carps was studied in three selected districts of Assam (India). The diseases incidences in fish varied with season with higher incidences during winter. Estimation of key water quality parameters and other predisposing factors i.e. high stocking density has a direct relation with MAS. Deterioration of water quality under suboptimal range during the winter season influences in the occurrence of MAS. A negative correlation of important water quality parameters i.e. temperature, pH, dissolved oxygen and alkalinity that indicated that fall in temperature, pH, dissolved oxygen and alkalinity influences on the occurrence of disease. While carbondioxide and ammonia were found to be positively correlated that indicated that increased value of ammonia and carbondioxide has a direct bearing on MAS. The regression of MAS (%) on water quality parameter was analysed. The functional relationship estimated by linear regression revealed positive and negative impact of water quality parameters on MAS with a coefficient of determinants ranged from 23.25 to 60.96 per cent. The data reveals that temperature had a negative impact on MAS b= (-2.69), p<0.01) indicating an increase of temperature by unit degree would lower MAS by 2.69 per cent. Similarly, increase in pH by unit degree would lower MAS by 12.16 per cent, unit degree increase in alkalinity would lower MAS by 0.41 per cent. Same way unit degree increase in DO and turbidity would lower MAS by 13.49 and 1.34 per cent, respectively. However, the scenario of CO₂ and ammonia was found to be reversed in which the value was positively correlated and revealed that for unit degree increase in CO₂, the MAS % was supposed to increase by 3.9 and 9.97 per cent in case of ammonia.