How Do Scientists Know Where the Fish Go?

Understanding where fish spend their time—including where and when they migrate—is an important part of scientists’ knowledge about species. But fish and other critters can’t just send a text when they get to their winter homes. As part of World Fish Migration Day, we want to share how scientists learn more about their movements.
NEWS
How Do Scientists Know Where the Fish Go?
Acoustic telemetry helps researchers keep tabs on individual fish and other critters as they migrate.
Feature Story New England/Mid-Atlantic 04/18/2018
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Tracking catfish movements helps understand impact on food webs. Credit: Smithsonian Environmental Research Center.

Understanding where fish spend their time—including where and when they migrate—is an important part of scientists’ knowledge about species. But fish and other critters can’t just send a text when they get to their winter homes. As part of World Fish Migration Day, we want to share how scientists learn more about their movements.

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Herring swimming.

Acoustic telemetry is one way scientists can fill in knowledge gaps; it is based on technology much like the microchips many pet owners have implanted in their furry friends. Those chips can be scanned using handheld devices at veterinarians’ offices or other animal care facilities, and the unique information the scan reveals can be used to find out the pet owner’s name and contact information in a database.

To use acoustic telemetry, researchers attach (either externally or via surgical implant) an electronic tag to individual fish. These tags emit a “ping” every minute or two that is a unique signal, essentially saying “I am fish #123.”

Receivers—small, data-logging computers—are located where researchers may want to learn more about fish in those areas. Then, when tagged fish swim near those receivers and emit pings, the receivers “hear” that they are there, and the presence of that particular fish is noted. Receivers can hear pings from as far away as a kilometer. Learning when individual fish swim near receivers can help researchers learn more about fish migration.

Currently, a number of agencies, including the U.S. Navy, and academic institutions maintain receivers. To get the data from most receivers, researchers need to physically connect with the receivers in order to download data.