EthoVision XT is the ideal tool to monitor fish movement, behavior, and activity in one or multiple aquaria, no matter what the aim of your research is.

• Increase your throughput and save time by monitoring fish in multiple aquaria simultaneously.
• Automatically measure apparent interaction between individuals in separate aquaria, by determining the time spent close to the side of the aquarium that borders the other individual’s aquarium.
• Automatically measure body mobility, in addition to a wide range of movement parameters.
• No need to concentrate on placing fish in their aquaria at the exact same time: EthoVision XT automatically starts tracking in an aquarium as soon as a fish is detected in that particular aquarium.
• Select data for analysis in order to calculate statistics on certain trials or fish, not others.

Introduction
Monitoring fish in multiple aquaria or tanks simultaneously is practical for several reasons. Obviously, tracking fish in multiple aquaria increases throughput and efficiency, saving time and effort. But for some research purposes, the ability to track animals in aquaria placed side by side simultaneously is invaluable in light of the research aim. For example, when investigating the effect of the presence of a conspecific organism, researchers often use separate aquaria with individual fish placed side by side. The separation eliminates chemical cues from the experiment and prevents physical contact between the individuals. Apparent interaction between individuals can be measured, while preventing possible injury.

If you want to track multiple aquaria simultaneously, no matter what the aim of your research is, Noldus can help you out. All you need is one EthoVision® XT software package loaded onto a computer and depending on the size of you aquaria, one or more cameras.

How it works
Depending on the research question, the video camera is positioned above or in front of the aquaria, each containing one fish. When interested in the distribution of time spent in the upper, center, and lower part of the aquarium, the camera is usually placed in front of the aquarium. When particularly interested in movement parameters such as swimming speed and total distance swum, a top position provides the best result. Minimizing the water level in the aquaria allows EthoVision XT to reliably and accurately measure movements. The video camera sends video images of all aquaria within its view to the computer running EthoVision XT. The software then tracks the paths of the individual fish and measures and analyzes a number of useful parameters.

You can program EthoVision XT to start tracking as soon as it detects a fish in an aquarium or as soon as any criterion that you defined has been reached. This general rule can be applied to each aquarium individually; when the fish has been detected in an aquarium, EthoVision XT starts tracking in that aquarium only. By using this cascading start option, you no longer need to worry about putting fish in their aquaria at the exact same time.

EthoVision XT measures a wide range of parameters related to swimming behavior, including swimming speed, distance swum, and percentage of time spent moving. In addition, a variety of parameters related to turning behavior can be measured. Mean turn angle indicates the change in direction and angular velocity measures the speed of direction changing. Both parameters can be used to analyze explorative behavior.

The aquaria can be divided in zones that you can later use to analyze your data. If you want to analyze behavior related to depth levels, the aquarium can be divided in horizontal zones. Subsequently, the time spent in the upper, center, and lower zone easily can be calculated. When investigating the interaction between fish in separate adjacent aquaria, vertical zones can be defined. The percentage of time spent in the zone close to the adjacent aquarium, while the other fish swims in the adjacent zone to the other aquarium, can serve as a measure of interaction.

Some fish species are known to lower the locomotor activity when chronically exposed to pollutants. To learn the differences between treated and non-pollutant treated fish, behavioral data from these two groups of fish needs to be compared. EthoVision XT allows you to select, analyze, and compare data belonging to each treatment group separately.