Effect of stocking density on water and soil quality, growth, production and profitability of farming Indian major carps

Abstract

Indian major carps (IMCs), catla (Catla catla); rohu (Labeo rohita) and mrigal (Cirrhinus mrigala) were cultured at stocking densities of 20000 (T1), 35000 (T2) and 50000 (T3) fingerlings ha-1 for a period of 300 days in nine numbers of polythene lined ponds having an average water area of 150 m2. Stocking ratio of catla, rohu and mrigal were 4: 3: 3. Fishes were fed 35% protein diet twice daily. Water pH was maintained within the ideal range (6 - 9) by intermittent liming. Significantly lower (p<0.05) levels of dissolved oxygen and higher values of total ammonia-nitrogen were recorded at higher stocking densities compared to lower ones. Significantly higher (p<0.05) specific growth rate (SGR) and lower feed conversion ratio (FCR) were recorded in T1 compared to T2 and T3. However, maximum production was recorded in T3 followed by T2 and T1. Highest values of investment as well as income were recorded in T3 followed by T2 and T1. However, the maximum net return was obtained in T1 (140147±7048) followed by T3 (133694±7931) and T2 (101944 ± 4857). Further, significantly higher (p<0.05) profitability (PI) was recorded in T1 (85.51%) compared to T2 (45.03%) and T3 (45.04%). The results clearly showed that profitability of the culture system could not be increased only by increasing stocking densities.