Researchers often use sound-emitting tags to keep track of fish, but are these devices drawing in predators? According to a study recently published in The Proceedings of the Royal Society B, acoustic fish tags may serve as a “dinner bell” to predators like grey seals. The study, which was conducted by researchers at the University of St. Andrews in Scotland, suggests that grey seals naturally hone in on the “pings” emitted by these tags, which could prove not only detrimental to the fish, but also impact the research that tags are being used for.
“Research agencies worldwide invest significant resources in acoustic tagging studies to assess fish stocks and determine survival rates,” the study stated. “As acoustic tags could make a fish more vulnerable to predation, tagging can lead to erroneous conclusions in such studies.”
In their experiment, researchers set up a maze of 20 foraging boxes in a pool. Half of these boxes contained a fish with a tag and the other half a fish with no tag. The researchers then let 10 seals into the maze and found that the predators consistently visited the boxes with a tag more than those without.
“This means that the seals learned to use the sound from the pinging tags to find where their food was hidden,” Amanda Stansbury, one of the study authors, told CBS News. “This tells us that seals can exploit new sounds, such as fish tags, and use them to their advantage.”
Researchers suspect that if the seals can do it, other predators can too. Not only that, but the fish themselves may have more trouble finding prey who are alerted by the tag.
“All tagging studies rely on the basic assumption that tags have no significant impact on marked individuals. However, our results suggest that acoustic tags could have profound effects on the fitness of the studied individuals in situations where they are audible to conspecifics, predators or prey,” researchers wrote.
It is also uncertain whether the ultrasonic pings emitted by tags will affect the fish they are attached to. The researchers suggested that further studies will be needed to investigate whether fish with tags behave differently as a result.