Abstract

<jats:p> A fast, simple, and reliable method for estimating food consumption using radioisotopes is presented. The method gives both sensitive short-term and robust long-term estimates of food consumption for brown trout (Salmo trutta). The estimates of daily food rations were similar to those estimated from rates of gastric evacuation and laboratory experiments. The radioisotope method can be used to detect variations in ration size due to temperature, fish size, and food availability. Information on radiocesium absorption from this study and earlier published data on radiocesium retention can be used to estimate daily ration for both piscivorous and benthivorous brown trout. The radioisotope method can be used in radiocesium-contaminated lakes, but it could also be used in other experimental situations by adding stable cesium to small water bodies. The same method is also applicable for use with other stable or radioactive isotopes. </jats:p>