What size of respirometer chamber fits my fish?
It is important that the volume of the respirometer chamber fits the experimental animal. If the volume is too large the resulting oxygen depletion curve will be too flat for reliable estimates of the slope that is used in the calculation of the oxygen consumption rate (MO2). A too large chamber will allow space for unwanted activity when trying to measure standard metabolic rate of an in-active (or static) animal. On the other hand, a large fish in a small chamber means that oxygen will decline rapidly to hypoxic levels which might affect the metabolism of oxyregulatory species. As a rule of thumb, we recommend a 1:10 ratio between the wet weight or volume of the fish and the volume of a static respirometer, e.g. a 500 ml respirometer volume for a 50 g fish, or a 10 liters respirometer volume for a 1 kg fish. NB: temperature affect metabolic rate in ectotherm animals like fish, e.g. high experimental temperatures favor the use of larger chambers and visa versa.
