Sanibel Sea School Blog
A Not-So-Silent Sea: How Fish Communicate Using Swim Bladders
Beneath the surface, a fascinating world of communication unfolds, where the seemingly simple swim bladder plays a pivotal role. Think of a swim bladder like a tiny balloon in bony fish (Osteichthyes). They can adjust the amount of gas in the bladder to control their depth – the more gas there is, the more they will float and vice versa. While this organ primarily helps bony fish control their buoyancy, in many species it also serves acoustic functions, including sound production and hearing.
Image Source: Saltwater Aquarium Blog
These acoustic signals vary across species and serve a multitude of purposes, including mating, navigation, and warning of danger. Creating and perceiving these sounds allows fish to share information that can be crucial for their survival and reproductive success.
Here are some of our favorites to listen to:
Sea Robins are known for their guttural, frog-like croaks. During mating season, however, they produce a staccato call that is different than the usual grunt. Listen here.
Image Source: Marine Biological Laboratory
“Drum” is a broad common name used for fish in the Sciaenidae family (black and red drum) that make drumming sounds. Southwest Florida residents living along canals frequently hear black drum calls at dusk during spawning season. Male calls sound more like a rumble or drum roll. Listen to the black drum here and the red drum here.
Catfish can make a symphony of sounds, including squeaks, growls, and grunts. They’re unique amongst noisy fish because they may use it as a form of echolocation. Listen to the hardhead catfish here.
Image Source: iNaturalist
All this noise has come in handy for researchers and conservationists. Turns out listening in on fish —or, if you want to get technical, passive acoustic monitoring (PAM) — is a great non-invasive way to census marine life. The most common reason for noise among fish is courtship and spawning, and many of these fish form large chorusing aggregations nightly, which can get pretty loud and are easily picked up by hydrophones. Researchers listen to these vocalizations, identify the species, and document the timing and location of spawning.
In Florida, snooping in on red drum allowed scientists to find spawning sites that fish have used for over 20 years! Long-term data sets like this allow scientists to track changes, which is especially important in coastal areas threatened by rapid development. Researchers can tell how spawning habitat changes over time in response to this and other variables, which is valuable information for developing natural resource policies.
Who would have thought a little noise would go a long way!
Contributing Author: Shannon Rivard
Sources & More Information:
Blaxter, J.H.S. (1981). The Swimbladder and Hearing. In: Tavolga, W.N., Popper, A.N., Fay, R.R. (eds) Hearing and Sound Communication in Fishes. Proceedings in Life Sciences. Springer, New York, NY. https://doi.org/10.1007/978-1-4615-7186-5_3