Metabolic utilization of body stores during the early life of whitefish, Coregonus lavaretus L.

Patterns of oxygen consumption, ammonia and urea excretion were monitored during late embryogenesis, i.e. 5 days before mass hatching and 12 days during the free-swimming stage of whitefish larvae, Coregonus lavaretus. Oxygen consumption increased from 1.31 to 2.53 mgO₂ h^?1× 10³ eggs^?1 at hatching. Fasted, free-swimming larvae showed increasing oxygen consumption to the tenth day after hatching when it reached 5.52 mgO₂h^?1× 10³ larvae^?1. Ammonia and urea excretion increased during pre-hatching period from 52.1 to 163.2 and 26.8 to 51.4 μgh^?1× 10³ eggs^?1, respectively. The nitrogen excretion rate increased between the sixth and tenth day of fasting, i.e. for ammonia from 117.7 to 160.9 and for urea from 35.8 to 52.5 μg h^?1× 10³ larvae^?1. Cumulative data on nitrogen and energy metabolism indicated that during late embryogenesis, and up to the fifth day after hatching, protein dominated in the energy expenditure. During the free swimming stage, the ratio of fat to protein in energy expenditure rose from 0.86 to 1.99. Combined data for several fish species indicated high dependance of oxygen uptake during the hatching period on egg size and temperature.