Water budgeting for production of hatchlings, fry and fingerlings of Asian catfish, Clarias magur

Studies were conducted to estimate the consumptive water use to produce hatchling (HL), fry (FY), and fingerlings (FL) of magur, Clarias magur in hatchery system. Aeration and water flow rate largely influenced the production of viable and deformed hatchlings in magur. In hatchling production, the HL-6 treatment group with 28 h water flow and 28 h aeration had the highest hatching rate (88%), followed by HL-5 with 28 h water flow (83%), whereas treatments HL-1 and HL-2 with 0 h and 14 h aeration, respectively, with no water flow failed to produce any hatchling. HL-6 had the minimal consumptive water use (CWU) of 530 +/- 11 litres for 1000 viable hatchlings production among the treatments. In 2nd study on rearing of larvae to fry with five water exchange schedules (25, 50, 75% daily, 75% in alternate days and 75% in two days once), significant differences in the growth and survival of larvae were observed among the treatments. Survival was significantly higher (98-99%) in the FY-1 and FY-2 treatment group with 25% and 50% water exchange daily, respectively. The most efficient CWU to produce 1000 fry was found to be 1068 litres (935 fry m(-3) water) for FY-1 with 25% water exchange daily. The 3rd study was conducted for ten weeks in outdoor tanks to optimize the water requirement for rearing of fry to fingerlings with 10, 20 and 30% water exchange per week. The highest growth (2.34 g) and survival (83%) (P < 0.05) were observed in FL-3 treatment receiving weekly exchange of 30% water. But in terms of water use and better survival rate, FL-2 water exchange (20%) group level showed the better survival rate (70%) and CWU of 5121 L for 1000 fingerlings production suggesting it to be the most water-efficient outdoor fingerling production system for magur.