Abstract
The oxygen uptake of cod (Gadus morhua L.) eggs is about 6 nl O2/egg per hour during the first 24 hours after fertilization. Uptake increases slightly but significantly until about 48 hours post hatching. A steep increase in the oxygen uptake then occurs, due to increased activity at the time of first feeding. At the time of final yolk absorption, day 6–8 post hatching, there is a peak value of 125 to ISO nl O2/larvae per hour in the oxygen uptake. A following drop in the oxygen uptake reflects the lack of nutrition in unfed larvae.
In halibut (Hippoglossus hippoglossus L.) larvae there is a homologous peak oxygen uptake of about 1100 nl O2/larvae per hour at the time of final yolk absorption (day 36–42 post hatching). The metabolic rate of the halibut larvae is about eight times that of the smaller cod larvae at the same developmental stage. This paper demonstrates the high reproducibility of closed respirometry in studies of the oxygen uptake of fish eggs and larvae. The reproducibility of this method is demonstrated trough seven different experimental long term series on cod during a period of five years.
