IN-SITU FOOD-CONSUMPTION BY YOUNG-OF-THE-YEAR BALTIC SEA HERRING CLUPEA-HARENGUS - A TEST OF PREDICTIONS FROM A BIOENERGETICS MODEL

Diurnal variation in stomach fullness of young-of-the-year (YOY) Balti c Sea herring Clupea harengus was used to estimate gut evacuation rate s and food consumption rates. The specific food consumption of these f ish increased with decreasing body length (25 to 84 mm) and increased with increasing temperature, ranging from 17 % of body weight d-1 in s ummer to 2 % d-1 at the end of October. The YOY food consumption rates do not differ significantly from consumption rates estimated from gro wth and a bioenergetics model (Rudstam 1988; Kieler Meeresforsch., Son derh. 6: 312-322) based on physiological data (respiration rates, eges tion and excretion) from adult fish. This result, and our earlier find ings, imply that the weakest points in estimating the food consumption of the Baltic Sea herring population are not bioenergetic assumptions , but assumptions related to YOY abundances, mortality rates and growt h rates.