Laboratory apparatus for studying the behaviour of organisms in vertically stratified waters

An aquarium system is described which was designed to examine the locomotor activity of juvenile salmon under simulated estuarine conditions. A stable, vertically stratified water column can be established and dissolved oxygen, salinity, water velocity, and light intensity varied during operation under continuous-flow or recirculating conditions. Examples of stratification stability and application to studies of fish behaviour in relation to hypoxia are also presented.