Tags on fish have a 'dinner bell' effect on seals, other predators

Researchers regularly attach acoustic tags to fish in order to track and study species as they move about their underwater environs, but it turns out those tags act like a dinner bell for nearby predators like seals.
The same high-frequency pings emitted by the tags and picked up on listening devices used by marine biologists are also detected by the ears of seals, offering the agile marine mammals directions to their next meal.
Because scientists understood seals to be capable of hearing a variety of sounds, (seals have been found to avoid human-specific noises), they theorized the mammals might be able to use pinging tags to their advantage. To test the hypothesis, researchers at the University of St. Andrews set of a maze of underwater boxes. Some boxes were empty, while others contained fish. One of the boxes contained pinging fish. Seals unleashed in the maze located the box of pinging fish much more quickly than the others.
"The seals found the tagged fish sooner and with less searching than the fish without a tag," Amanda Stansbury, a researcher at the university's Sea Mammal Research Unit, explained in a recent press release. "This means that the seals learned to use the sound from the pinging tags to find where their food was hidden. This tells us that seals can exploit new sounds, such as fish tags, and use them to their advantage."
Standbury and her colleagues say the results of their study prove researchers need to be more aware of the unattended consequences of their research.
"We expect that other marine mammals are similarly able to use such information to find prey," she added. "Tagged fish may be more detectable by predators, which could affect the results of fish studies."
The study's results were detailed this week in the journal the Proceedings of the Royal Society B.