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  Acoustic Tags  > What are acoustic tags? What is acoustic telemetry?
  Acoustic tags are small sound-emitting devices that permit remote tracking of fish in three dimensions. Commonly used to monitor the fine-scale behavior of fish, studies are conducted in lakes, rivers, estuaries, at dams, and at sea. HTI’s acoustic telemetry is tag tracking technology that allows researchers to view 3D fish tracks in real-time in high-resolution. Literally hundreds of fish can be tracked simultaneously and the positioning data is most often accessed remotely via satellite.
> How do acoustic tags work? Concept of fish "pinging" through hydrophones Click the above to view animation of acoustic tag
 "ping" concept.

Acoustic Tags transmit an underwater sound signal or acoustic "ping" that sends identification information about the tagged fish to hydrophones (hydrophone). By determining the sound's time of arrival at multiple hydrophones, the 3D position of the fish can be calculated, in a manner similar to how GPS is used to calculate positions. The hydrophone receiver receives the sound signal and converts it to digital data that researchers use to plot the resulting tag positions in 3D, in real-time. Post-processing software, MarkTags takes that data and delivers the end result, the 3D track.

> How long can I track fish movement? And how many fish at one time?
How can I track fish movement or behavior?
 Unique to acoustic tags is the capability to have up to 62,000 user-specified
   individual tag ID codes with battery lives over 3 years. Detection ranges are
    up to 1 km (3,280 ft) in fresh water. The transmitted tag signals can be encoded     for maximum strength to improve range and resolution. Thus, an array of     receivers allows the researcher to record the movement of a particular fish
   (in presence/absence mode) over many kilometers. These variables allow a    custom fit for each unique project. email HTI home site map Over 500 Model 795 Acoustic Tags within  range of a Model 290-series Receiver can be tracked simultaneously. Are acoustic tags best for my study?
> What are the advantages of acoustic tags over radio tags?
  Acoustic tags have several advantages over radio tags for tracking fish and other animals in water. Unlike radio tags, which are typically only detected within the first 10 m (32 ft) of the surface, acoustic fish tags detect fish movement anywhere in the region of interest within the detection range of the tag [up to 1 km (3280 ft)] in freshwater.

Read the list of advantages and disadvantages to find out key factors to consider before starting your research.
> Which tag is best for my fisheries research? Are acoustic tags best for your study? Take a quick survey to find out.
  It depends upon the variables. Acoustic tags are produced in many different sizes depending on the type of species being studied, the tag life required, or the type of environment in which the study is conducted. Sound parameters such as pulse width and signal encoding are chosen for optimal signal level, and detectability. Longer tag life can be obtained by changing operating parameters (i.e. pulse width, pulse reception interval), or by using large tags.
 > What are acoustic tags?
 > How do acoustic tags work?
 > For how long? How many?
 > Advantages over radio tags
 > Which tag would be best?
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