Effects of pre‐ and post‐prandial starvation on meal size and evacuation rate of juvenile Atlantic salmon, Salmo salar L.

After a pre‐prandial period of starvation or feeding with unlabelled food, 0+ salmon parr (0.8–11.7 g) were fed a test meal of iron particle labelled food and subsequently were again either starved or fed unlabelled food. The quantity of labelled food consumed and the evacuation rate was determined by serial radiographs. In fish of all sizes, pre‐prandial starvation causes a larger test meal (as a percentage of body weight) to be consumed when compared to pre‐prandially fed fish. In addition, pre‐prandial starvation results in relatively larger meals as a percentage of body weight being taken by smaller compared to larger fish. This result was not evident for pre‐prandially fed fish. Evacuation rate was unrelated to body size irrespective of feeding history. Post‐prandial starvation decreased evacuation rate but this effect was inversely related to the quantity of food consumed. Larger meals were not evacuated differently from smaller meals if feeding occurred post‐prandially, irrespective of pre‐prandial starvation.