• Wilder, I.B.
  
• Stanley, J.G.
  

Free nucleotides, RNA, and DNA were extracted from fish white muscle and analyzed by a two-wavelength ultraviolet (UV) absorbance technique to determine their relation to growth rates in brook trout, Salvelinus fontinalis, and Atlantic salmon, Salmo salar in the laboratory, fish given ample feed had higher growth rates than fish on restricted rations, and these growth rates were significantly correlated with RNA-DNA ratios. Wild brook trout from natural streams had higher average RNA-DNA ratios than those in the laboratory. Exposure to brook trout in one of the streams to low levels of the insecticide carbaryl (Sevin) that drifted from the spraying on nearby forests did not reduce RNA-DNA ratios.