Effect of periphyton diet on the growth of snow trout, Schizothorax richardsonii (Gray)

One year experiment was conducted in three raceways of the size 8.73m x 1.63m x 0.84m with a view to develop diet for an indigenous cold water fish, Schizothorax richardsonii (Gray). Prior to growth experiment Periphyton biomass was developed in the raceways by using plastic sheets and bamboo splits as suitable substrates. First group of the fish was fed with formulated artificial diet having 25% crude protein @5% of their body weight as control. Second group of the fish was fed with exclusive natural periphyton based diet. The third group was fed with combined feeding of formulated artificial diet @ 3% of their body weight as well as the natural periphyton diet. Artificial diet and periphyton diet were analysed for proximate composition. Acclimatized healthy Fry of snow trout having the average weight 1.11?0.04 to 1.85?0.07g.were stocked @8-10 fry/m2 in raceways. The ranges of water quality parameters recorded in different raceways were: temperature 12.0-20.0°C, pH 7.0-8.5, DO content 6.0- 8.0ppm, free CO2 2.0- 2.4 ppm and total alkalinity 167-170 ppm. All Physico- chemical parameters were in acceptable range for the growth of snow trout. The highest average final weight (21.9 g) of snow trout was found in the raceway (R3) having combined supplementary feeding and natural periphyton diet with total production as 2.540 kg. (18.14 kg/100m2/yr) and 97% survival. The average final weight of the fish was 47% more than the control (R1), while the total production was 57.9% higher over the control. SGR in R3 was 3.05, which was 47.8% more than the control with FCR as 3.74.The values of K were recorded in the range of 0.931, 0.951 and 0.991 in Raceway R1, R2 and R3, respectively. An income of Rs.2408/100m2/yr with combined feeding, while it was Rs. 1980/100m2/yr with artificial feeding alone. These results indicated that combined feeding with formulated feed of 25% protein level and natural periphyton diet may be useful for profitable culture of snow trout in hills.