Food intake and seasonal changes in energy content of young Baltic Sea sprat (Sprattus sprattus L.)

Diel variation in stomach fullness of O-group Baltic Sea sprat (Sprattus sprattus) was used to estimate gut evacuation rates and food intake rates. Daily food intake decreased with increasing body length from 35 to 84 mm, ranging from 11% of body wet weight d(-1) in August to 2% in the beginning of November. Young sprat undergo seasonal and yearly fluctuations in body composition. There was an increase in energy density between August and December, from 3700 to 5300 Joules g(-1) wet weight. The actual food intake rates differ significantly from the rates estimated from a bioenergetics model based on parameters from a mixture of young and adult clupeids. The reliability of using the bioenergetics model for food intake is discussed. (C) 1998 International Council for the Exploration of the Sea.