An apparatus for testing the effects of episodic stressors on juvenile and adult fishes

We describe an apparatus designed to deliver pulsed changes in water quality with variable (and controlled) magnitudes, rates and durations. The apparatus combines both standard flow-through and recirculating systems, and it is designed for use with six 1141 aquaria. All components are of standard materials and sizes, and customizing to fit existing systems is easily accomplished. The apparatus has been used to simulate the dramatic changes in salinity associated with freshwater canal discharge into Biscayne Bay, Florida. An example of its application on juvenile bluestriped grunts (Haemulon scurus) is presented. Although we focus here on salinity fluctuations, the apparatus could also be used to examine the effects of other variables (e.g., temperatures, turbidity, and contaminants) with little or no modification to the system.