The gastric evacuation rate (GER) of fish means the speed of food evacuated from stomach after feeding. It's usually used, in combination with the contents in stomach of fish sampled continuously in situ, to estimate some important ecological parameters, such as daily ration, feeding periodicity and ecological conversion efficiency. Because the parameters obtained by above method are closer to natural state, many studies published since 1960's have focused on GRE. As the principal consumer of zooplanktons a...