Hydroacoustic Technology, Inc.
  Hydroacoustic Technology, Inc.    
  Acoustically Tagging American Eels: A Case Study  
University of Massachusetts


  Massachusetts U.S.A.

  "This study enabled us to obtain detailed, previously unknown behavioral responses of eels to forebary conditions." Dr. Alex Haro, Professor, University of Massachusetts  

Over the last two decades, scientists have found the abundance of American eel (sp. Anguilla rostrata) in the northwest Atlantic in serious decline. Many factors contribute to the decline but, to what degree?

Information about eel behavior passing down-stream through dams has been limited. However, in 2003, a graduate student at the University of Massachusetts (Leah Sullivan) used acoustic telemetry to investigate their behavior along the Connecticut River, at one of the numerous north eastern hydro-electric facilities.

Fifty eels were surgically implanted with HTI's Model 795 Acoustic Tags and their movement was monitored in 3D in the forebay (the first 100 m of area located directly upstream of the project). The study helped shed light on how the eels were choosing to pass the dam. Each eel’s 3D location was revealed every 3 seconds. Resulting tag positions were plotted in 3D revealing the fine-scale movement of each eel.
It was discovered that the eels occupied a variety of depths throughout the forebay; however, most their of time was spent near the bottom. The eels occupied the middle and upper water column more frequently and displayed an increase in turning movement immediately upstream of the trash racks. The increase in surface orientation and elevated turning angle was the result of the eel’s vertical and horizontal searching behavior in this area.

Most frequent behaviors included quick, upstream movements after eels encountered the trash racks, vertical and horizontal changes in position at or near the trash racks. Eels appeared to be volitionally choosing the turbines as their preferred downstream passage route based on dominant flow. To view a few clips from the 3D tracks, please see tracks above right.

3D tracks of American eels passing downstream at a dam.
Click to view animations.
Acoustic Tagged Eel Track 1 Acoustic Tagged Eel Track 2  
Acoustic Tagged Eel Track 3 Acoustic Tagged Eel Track 4  
Inserting the acoustic tag into the anethesized eel. On-site at release of acoustically tagged eels.  
Inserting the acoustic tag into the anethesized eel. On-site at release
of tagged eels.
  Data from Acoustic Tag Software
If you have questions about tracking eel survival, behavior, or migration patterns, HTI offers acoustic telemetry equipment for 2D and 3D tracking and fisheries consultants to conduct research. Email HTI to get a recommendation.
American eels (Anguilla rostrata). Releasing eels into the Connecticut River.  
American eels
(Anguilla rostrata).
  Releasing eels into the Connecticut River.  
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