Gastric evacuation rates of brook trout

We estimated the gastric evacuation rate (GER) of brook trout Salvelinus fontinalis at five different temperatures (4.3, 9.1, 12.1, 15.6, and 17.0degreesC). Fish were fed a mixed meal of fly larvae and beetle larvae, and stomach contents were sampled by gastric lavage at various times over a 48-72-h period to determine the proportional dry weight of an initial meal remaining in the stomach after feeding. The relationship between the proportional amount of a meal remaining in the stomach and the time postfeeding was best described by a linear function over all temperatures. As temperature increased, the instantaneous rate of gastric evacuation increased, but the rate of increase slowed at temperatures greater than 12.1degreesC. Brook trout GERs were much lower than those reported in the literature for other species at similar temperatures. These data will be useful for future field studies attempting to estimate daily ration.