Juvenile Eel and Lamprey Acoustic Transmitter

Battelle Number: 30972 | N/A

Technology Overview

Populations of the American eel and lamprey are declining. Numbers of these two species have dropped significantly over the past 40 years in the Columbia River basin and elsewhere in the country likely due, in part, to hydropower facilities that block their passage downstream. The American eel is proposed for listing under the Endangered Species Act.

Understanding more about how these long-bodied fish move and behave are key to their survival. To get that information, PNNL has developed the smallest acoustic transmitter (tag) ever--designed specifically for juvenile lamprey and eel, and other small fish and early life stage studies.

Tracking the movement and behavior of these younger, smaller fish in their natural habitat is more challenging than other species and adults. But this information is necessary to develop mitigation strategies for helping them maneuver around dams and migrate downstream.

A Leader in Development of Acoustic Telemetry Systems 

PNNL researchers have extensive experience in creating acoustic telemetry systems for a variety of fish species. These systems involve implanting a small tag, powered by an even smaller battery, and a transducer into the fish. The tags send out an acoustic signal or ‘ping’ to receivers, typically located along riverbanks. The researchers work began with salmon, then juvenile salmon and other species, and resulted in a suite of technologies. But the tags were all too large for the juvenile eels and lampreys that migrate downstream to the ocean to grow into adulthood.

An even tinier tag and power source specifically for studying the very thin, flexible juvenile eel and lamprey was developed by researchers. The tags were manufactured at PNNL's accredited Bio-Acoustics & Flow Laboratory and field tested in various environments, including the fast moving Columbia River, a forebay just upstream of Roanoke Rapids Dam in North Carolina, a tailrace carrying water away from a dam on the Potomac River, and in shallow water in a North Carolina creek.  

The very tiny tags were surgically implanted through an incision less than 3 millimeters long--so small that it does not require sutures. The trials conducted on juvenile lamprey and eel indicated that tags implanted in both species did not affect their swimming ability or survival. There also is minimal tag loss over the test duration of 30 days.


Tiny Tags Differentiate PNNL  

Prior to this development, existing acoustic tags were too large to be effectively implanted into the body cavities of juvenile eels and lamprey and would result in a tag burden that exceeds accepted standards. Information on juvenile lamprey passage, survival, or behavior is very limited. With the smaller PNNL acoustic tag, collecting data will be easier.

PNNL is establishing partnerships with hydroelectric facility operators and agencies interested in further developing and demonstrating this technology. Behavior and movement data acquired from the tags will be used to inform the design of future hydro turbines and mitigate current operations to reduce injury and mortality for the fish.

Better insight could be used to develop additional mitigation strategies to help the eel and lamprey move downstream, including new designs of bypass systems at hydroelectric facilities and irrigation diversion structures. Other possible benefits of using acoustic tags to study juvenile eel and lamprey movements include the ability to estimate survival, fallback rates at spillways or via turbines, re-ascension rates, passage delays, behavior as fish approach dams, and travel time within reservoirs or free-flowing river systems.


  • Better for fish due to small size
  • Enables early life stage studies on smaller and younger fish
  • Implantation does not require sutures
  • Reduced amount of time required for surgical incision
  • Faster healing rates
  • Decreased possibility of infection at implantation site
  • Extremely lightweight¾approximately 0.08 grams in air
  • Smallest acoustical tag
  • Length 12.0 millimeters
  • Diameter: 2.0 millimeters
  • Transmitter life: Prototype lasts 40 days at a 5-second ping rate interval


Available for licensing in all fields


hydropower, American eel, Lamprey, acoustic transmitters, fish tracking, hydropower, fish tags, telemetry



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