Saini, V. P.KUMAR, VIJAY2019-02-072019-02-072018Kumar. V, and Saini. V.P.http://krishikosh.egranth.ac.in/handle/1/5810094016Effect, water hardness, egg hatchability, larval viability“Effect of water hardness on egg hatchability and larval viability of Labeo rajasthanicus” Vijay Kumar* Dr. V. P. Saini This study was conducted to assess the impact of water hardness on egg hatchability and larval viability of Labeo rajasthanicus.For this purpose,five hardness levels were tested (200, 175, 150, 125, 100 mg/l ) in relation tofertilization rate, ova diameter, hatching duration, hatching per cent and hatchling survival of Labeo rajasthanicus. For incubation of eggsa simple hatchery device was fabricated. In each hatchery jar 5000 eggs ware incubation & each treatment was run in triplicate. The diameter of egg was measured using Leica microscope with computer based software. The smallest (3.33 mm) ova diameter was observed in T1(200 mg/l), whereas the biggest (3.54 mm) ova diameter was in lowest water hardness level (T5-100 mg/l).The Minimum hatching time (15.45 hrs) was noticed in lowest hardness treatments (T5),which was significantly increased with increasing hardness level and the highest hatching time was recorded in highest (200 mg/l) concentration of hardness. The highest hatching rates (95%) occurred in groups of eggs that were hardened in the softest water treatment (100 mg/l), whereas the lowest hatching rates (69%) was in T1 (200 mg/l). The highest larval survival (79.46%) was recorded in 200 mg/l water hardness and lowest larval survival rate (65.71%) was found in 100 mg/l hardness. Further, the survival rate had positive relationship with hardness as the rate of larval survival significantly increased with increasing water hardness.Overall results suggested that the water hardness 125 - 150 mg/l is the ideal for egg incubation of L. rajasthanicus for higher fertilization rate, better hatching percentage and more larval survival. These results may be a prelude to effectively utilize the benefits of hardness on better hatching rate and ultimately the cost of production in carp hatcheries.ennullThesis