RNA-DNA ratios as an indicator of fish growth in golden mahseer (Tor putitora)

Abstract

In this investigation, Golden Mahseer (Tor putitora) having an average body weight ranging between 3.5 and 650 gms were collected from Experimental Mahseer Hatchery and lake, Bhimtal in order to assess the food availability in their natural habitat as well as for the prediction of growth rate. Commonly used molecular indices for fish growth and feeding conditions include RNA concentration (µg/mg tissue) and its ratio to DNA (RNA/DNA). Most of the isolated DNA had no sign of degradation and the spectrophotometer analysis of absorbance at 260 and 280nm provided ratios ranging between 1.70 and 1.90 indicating that quality of DNA was good. The DNA and RNA concentration ranged between 4.06 and 8.86 and 0.92-to 23.70 µg/ mg respectively. The RNA/ DNA ratios ranged from 0.10 to 4.83 with the mean average of 2.52. The means of the RNA/ DNA ratio of the wild fish were relatively higher than that of the reared fry indicating that they were generally in better condition. A positive correlation was also observed between body mass/size of the fish with RNA/ DNA ratio. The RNA concentration and ratio of tissue RNA/ DNA have proven to be a reliable estimator of recent fish growth rate and food availability in their natural habitat.