RNA-DNA ratios in white muscle tissue biopsies reflect recent growth rates of adult brown trout

Recently developed fluorescence techniques were used to quantify RNA-DNA ratios in white epaxial muscle tissue biopsies taken from live adult brown trout. RNA-DNA ratios from small biopsies (4-24 mg wet weight) were measured concurrently with growth over 5 weeks in two groups of brown trout fed different rations, 5% BW day(-1) (reference) and 1% BW week (treatment). Reduced rations had significant effects on RNA-DNA ratios in muscle tissue biopsies. The treatment group had significantly lower mean RNA-DNA ratios than the reference group after the first week. After 5 weeks of treatment the mean RNA-DNA ratios of the treatment and reference groups were 1.98 and 4.31, respectively. RNA-DNA ratios from muscle tissue biopsies reflected recent growth rates in the two groups of fish. This technique allows a biochemical measurement of growth rates in adult fish without mortality. (C) 1996 The Fisheries Society of the British isles