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 (Spratt us sprattus) was used to estimate gut evacuation rates and food intake rates. Daily food intake decreased with increasing body length from 3 5 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 dens ity between August and December, from 3700 to 5300 Joules g(-1) wet we ight. The actual food intake rates differ significantly from the rates estimated from a bioenergetics model based on parameters from a mixtu re of young and adult clupeids. The reliability of using the bioenerge tics model for food intake is discussed. (C) 1998 International Counci l for the Exploration of the Sea.