Comparison of quantitative light microscopy techniques used in diet studies of detritus-consuming omnivores

The assumptions and performances of three light microscope techniques for measuring the amount of detritus in the diets of omnivorous fish were compared: area estimation, volume estimation with subsequent estimation of weight, and weight difference determination. Accuracy of the area method depends on the improbable assumption that the volume or weight of detritus particles in the diet is directly proportional to particle area. Accuracy of the difference determination is limited by the accumulation of measurement errors associated with each component of the calculation. Direct estimation of volume with subsequent conversion to ash free dry weight requires the fewest assumptions and offers greatest accuracy. Precision was greatest for the volume estimation technique and lowest for the difference determination. Time required per sample can be substantially reduced by using a digitizer for measurement and a microcomputer for calculations