When studying social interaciton in fish, you need to be able to score behavior in great detail, while dealing with quickly moving animals. That is where The Observer XT helps you out. 

• Code detailed social behaviors rapidly and automatically calculate statistics.
• Score behavior live or from previously recorded video files, using the sampling method of your choice: continuous or interval.
• Concentrate completely on the fish and their behavior; The Observer XT automatically adds time stamps to the logged events.
• Playback those parts of the video in which a lot of interactions occur and take a second look or score in more detail. 
• Select data for analysis in order to calculate statistics on specific observations, fish, or event types.
• Make clips of the video parts of interest to you.

Introduction
Social interaction is a major field of interest in research on fish. Topics include sexual selection mechanisms, effects of rearing conditions in intensively-kept farm fish, and relationships in complex breeding species. All these studies all have one thing in common: interaction behaviors need to be observed with high detail in quickly moving animals.

Noldus provides you with the perfect tools for this type of research. Combine The Observer® XT with our hardware and services, and you have the ideal solution for investigating social interaction in fish. In The Observer XT, detailed behaviors can be easily logged, either live or from previously recorded media files. The Observer XT automatically adds time stamps to the logged behaviors and calculates various statistics.

How it works
Start your experiment by designing a coding scheme (ethogram) on the computer running The Observer XT. This coding scheme should contain each behavior and each fish you want to study, including their corresponding codes. During scoring later on, you still have the option to edit this coding scheme. Consider if you want to score behaviors live, while they occur, or offline from previously recorded video material. Because you are dealing with quickly moving animals, it is often important to score in some detail, and offline scoring might be the most practical method. The advantage here is that you can playback the video at half speed, making scoring a lot easier. The Observer XT also gives you the opportunity to score live, and acquire video at the same time, so that you can always look back and check, or score in more detail later on. 

Scoring behaviors is done simply by pressing the corresponding key of the keyboard or clicking on the behavior in the coding scheme. The Observer XT automatically adds time stamps and calculates statistics, such as the total number and duration of display behavior by the male fish or the percentage of time in which the dominant fish was chasing a subdominant individual. If you want to add extra information to your observations, you can add independent variables, such as gender of the observed fish. You can also link so-called ‘modifiers’ to behaviors to add more detail. When investigating aggression, for example, the behavior ‘display’ can be extended with the modifier ‘side’ and modifier values ‘frontal’ and ‘lateral’. When observing fish in a large group, the behavior ‘bite’ can be extended with the modifier ‘subject’ and the ID of the fish being bitten as modifier value.

When you are studying social  interaction in fish, you will  likely have many observations. Scoring behaviors can be time  consuming and therefore it  is useful to consider setting  up a multiple coding station  configuration. Several observers  can score at the same time  using The Observer XT Coder Licenses. These licenses are costeffective  and limit the use of The Observer XT program to scoring and  visualization only. After all behaviors are scored, you can collect the  observations in your main project with a full license and perform data  selection and analysis.

After all observations are completed,  The Observer XT allows  you to select data based on  subjects, behaviors, observations,  or independent variables,  prior to visualization or analysis.  This way, you only use the  data that you are interested in.  For instance, you can select all  data belonging to the breeder  male or all data belonging to  female individuals and only subject this data to analysis. In social  interaction research, it is often important to know what happened  during a certain period of time or behavior. For instance, you might  want to analyze the frequencies and durations of beha-viors related  to caring for the nest of the female fish while the breeder male was  chasing other males away from the nest. The Observer XT allows you  to analyze your data to different extents: from basic classification to  in-depth selection and analysis.