RESPIROMETRY-Scientific Context
A swimming chamber enables us to measure the effects of low oxygen levels on metabolism and swimming activity of cod. Its design and the possibilities it offers make this instrument very interesting for our work.

Work on oxygen, metabolism and swimming date back many years. After experimenting with static systems where oxygen uptake was measured at rest in closed systems, the next step was to do similar measurements during activity. This approach is not new and various types of instruments have been used which are adapted to various fish species, from the very small (sticklebacks) to the very large (tunas). After an extensive literature review and after consulting with other laboratories, a Blaza-type system was chosen and adapted for use with cod up to 50 cm in length. The instrument used at the MLI enables us to film the fish while it is swimming at different speeds and to detect changes in swimming pattern. Water velocity and hence swimming velocity can also be controlled. Thus we can subject fish to a controlled swimming exercise under different experimental treatments. The system also enables us to measure the oxygen uptake (metabolic rate) of a resting or swimming fish. It is therefore possible to measure how a variable, such as temperature, affects the metabolic rate and the swimming capacity of a fish. All these measurements can be made in a closed or open system. It is also possible to vary the oxygen concentration to simulate the various underwater environments of the Gulf and estuary. Coupled with the automatic data capture system and video system, this instrument is highly versatile.