Satiation and gastric evacuation in juvenile masu salmon.

The satiation time, the satiation amount and the rate of gastric evacuation for juvenile masu salmon Oncorhynchus masou having various sizes were determined at two different water temper-atures (16.2-16.8°C and 8.6-9.4°C). When there was an excess of food, the satiation time was less than 60 min, with a tendency to increase with increasing fish size in both water temperatures. The satiation amount was proportional to W0.715 (W: fish body weight), independent of the water tem-perature. A square root model was more suitable for estimating the gastric evacuation rate than an exponential model. The rate of gastric evacuation for high water temperature was greater than that for low water temperature. From the results of statistical analysis of the difference in the regression parameters between the sized groups, the instantaneous rate of gastric evacuation was constant with respect to the fish size, while the evacuation time was longer in the smaller fish, which consumed a larger meal per unit body weight than in the larger fish.