Females Listen to Male Chirps : Talking Fish Use Husky Voices to Lure Mates

Scientists have discovered that damselfish recognize each other by their voices and that at spawning time the male with the lowest voice is considered the sexiest partner on the reef.

The female damselfish chooses a mate by listening to the chirps of the males. There is a direct correlation between the animal’s size and the peak frequency of the sounds it makes.

Since the male damselfish watches over the eggs until they hatch, the female will pick the largest male available in order to give her offspring the best chance for survival on the reef.

“The lower the voice, the more sexy he is,” said Dr. Arthur Myrberg, a researcher at the University of Miami’s Rosentiel School of Marine and Atmospheric Science.

Damselfish also use their voices to defend their homes. They are territorial and make certain sounds that other fish recognize as “keep out” noises that mean the turf is claimed.

Condition Fish

In the laboratory, Myrberg and his associates have been able to condition male damselfish to come to a particular area of the tank when one sound is played and to leave the area when another sound is played. The two sounds are identical except for a slight difference, 20 to 30 hertz, in peak frequency.

In the fish, a pitch difference this small would correspond to a size difference of less than one-eighth of an inch.

“Since all animals vary slightly by size, this means that damselfish can recognize individuals by their sound alone,” Myrberg said. “Fishes are doing that which we often do: They recognize individuals by factors associated with spectral frequency. They tune in to the pitch of an individual’s voice in order to recognize it.

“We have been able in the last several years to control the behavior of fishes on the reef as well as in the lab, through the use of sounds. We have been able to increase courtship behavior. We can force females to spawn with males they normally would not have spawned with based on transmitting sounds near that male.”

The damselfish, a colorful fish usually 3 to 6 inches long and found on reefs throughout the Caribbean and the Bahamas, was chosen for the experiment because it is highly vocal. But the researchers believe the ability to distinguish subtle differences in frequency is possessed by many, if not most, species of fish.

Fish sounds are generally made up of rapid pulses of sounds, a sort of “thpt, thpt, thpt.” The air space in the human ear makes it difficult for people to hear these sounds without an underwater microphone, but the fish have no such difficulty, Myrberg said.

Shark Hearing Tested

He and other Rosentiel researchers have extensively studied the acoustical biology of marine animals and are also investigating hearing in sharks.

Myrberg is not certain how the research will be used.

“It is not something we can immediately hook a practical or applied aspect to. This simply demonstrates that tiny animals on the reef have quite sophisticated communication capabilities. It will hopefully lead to greater knowledge and understanding of the process,” he said.

Myrberg’s research has earned him a reputation as “the man who talks to fishes.”

“They talk back, but they’re not talking back to me,” he said. “The ocean is a very noisy world. It is a very important system for not only communicating between individuals but for intercepting signals. There are other animals listening. Certain predators are attracted to these sounds. It is a trade-off.

“The damselfish is obviously wishing to communicate with individuals of the opposite sex or members of their own sex but must take into consideration that it is also rather dangerous.”