Abstract
Gastric evacuation of groups of juvenile (mean 63 mm total length, L T , 0·283 g dry mass, M D ) sprat Sprattus sprattus feeding on brine shrimp Artemia sp. nauplii was studied at six temperatures (7·5, 10, 13, 16, 19·5 and 21·5° C) in the laboratory. Gastric evacuation was best described with a general model: , with S t = stomach content at time t , S 0 = stomach content at time 0, t = time , R , B = constants. The shape parameter was estimated as B = 0·668. For comparison with other studies, an exponential model was fitted also to the data. The evacuation constant ( R ) of the general gastric evacuation model increased exponentially with temperature between 7·5 and 16° C. The slope of the increase was reduced between 16 and 19·5° C and a slight decrease was observed between 19 and 21·5° C. Additionally, the effect of mean M D (range 0·286 – 1·025 g) was examined. A simple power function ( ) described the influence of predator mass on exponential evacuation constant with C = 0·503. The results of this investigation were integrated into a consumption model for the calculation of daily rations of S. sprattus : , with T = ambient temperature (°C) and of field stomach contents (g dry) individually raised to the power of 0·668.