These Spiny Lobsters Make Sounds That May Be Detectable Nearly 2 Miles Away

Sounds produced by European spiny lobsters may be detectable up to nearly two miles (around 10,500 feet) away from the animals, researchers have suggested.

These crustaceans make loud rasping sounds underwater by rubbing the bases of their antennae for the purposes of communication or warding off predators.

To understand more about these so-called "antennal rasps," a team of researchers recorded more than 1,500 of the sounds produced by 24 spiny lobsters (Palinurus elephas) in the Bay of Saint Anne du Portzic, France.

They did this using a set of underwater microphones, known as hydrophones, located at distances between 0.5 and 100 meters (1.6 to 328 feet) away from the crustaceans, which varied in size.

According to a study published in the journal Scientific Reports, the sounds produced by the smallest lobsters could only be recorded at distances of up to 50 meters (164 feet.) However, the larger lobsters involved in the study produced sounds that were detectable at a distance of 328 feet.

By examining how the intensity of the sound decreased over distance, and taking into account the high ambient noise levels in the water of the Bay, the scientists estimated that the antennal rasps produced by large European spiny lobsters could potentially be detected up to 400 meters (1,312 feet) away.

Furthermore, they suggest that the very largest specimens—in this case, those measuring more than roughly five inches in length—likely produce sounds that may be detectable up to 3 kilometers (1.86 miles away) under different conditions, for example, in water with lower ambient noise levels than the Bay.

European spiny lobster
A large spiny lobster held by a scuba diver during an acoustic experiment. Erwan AMICE© cnrs

"Interestingly, the closest animals with this kind of sound-producing apparatus do not live underwater but on land—the insects. Spiny lobsters are notably closely related to crickets, which has led to them being nicknamed 'sea crickets' by fishermen," Youenn Jézéquel, lead author of the study from the Laboratoire des Sciences de l'Environnement Marin, told Newsweek.

"The intensity of these antennal rasps makes the spiny lobsters the second loudest crustacean species ever reported in marine ecosystems, with the antennal rasps produced by the largest spiny lobsters being more than 170 decibels at less than one meter from the animals," she said.

European spiny lobsters are among the most highly-prized gourmet seafood around the world, with the species being sold at markets on the continent for between €40 and €120 ($44 to $132) per kilogram (2.2 pounds,) according to a separate study also published in the journal Scientific Reports.

However, decades of overfishing have contributed to considerable population declines since the 1970s, particularly in the Mediterranean Sea, leading to the animal being classified as "Vulnerable" on the International Union for Conservation of Nature's Red List of Threatened Species.

The authors of the latest study say the new knowledge that the antennal rasps can be detected at large distances may have important implications for conservation efforts. This is because the use of non-invasive techniques—such as underwater sound observations—could form a crucial part of initiatives to monitor and survey this vulnerable species in coastal waters.

"To date, most conservation efforts have used highly invasive and destructive trammel nets to estimate their population densities and distributions underwater. In this context, it is critical to find new non-invasive and non-destructive tools to study this species in its natural environment," Jézéquel said.

Previous research has revealed that crustaceans emit a wide array of sounds underwater, like many other marine animals. However, there is relatively little data on how sounds made by crustaceans travel through the water, according to the authors of the latest study.

While the researchers were able to detect the antennal rasps more than 300 feet away using the underwater microphones, they speculate that the sounds may not actually be audible to the lobsters over these distances.

Determining how far away the lobsters can hear each other is difficult because little is known about their hearing abilities. But using the available information the researchers estimate that they might be able to communicate over distances of no more than 10 meters (32 feet,) which is similar to what is known for fish.

European spiny lobsters are found in the waters off the coasts of Great Britain and Ireland, as well as in the Mediterranean, up to depths of around 650 feet.

This article was updated to include additional comments from Youenn Jézéquel.