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> What are acoustic tags? |
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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 tag tracking technology allows researchers to view 3D fish tracks in real-time with sub-meter resolution. |
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| > How do they work? |
 Click the above to view animation of acoustic tag
"ping" concept.
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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. |
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| > How long can I track movement? And how many can be tracked at one time? |
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Unique to acoustic tags is the capability to have up to 100,000 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.
Over 500 Model 795 Acoustic Tags within range of a Model 290-series Receiver can be tracked simultaneously.
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| > What are the advantages of acoustic tags over radio tags? |
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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 learn more. |
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| > Which tag is best for my application? |
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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. |
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