What noises can fish make?
Hello fish, this is a really interesting topic because fish bioacoustics is actually a whole research field, and there are many different mechanical solutions fish have evolved to generate sound. I will focus on how the sounds are physically produced as we already talked about what they are mostly used for in communications.
Fish do not have vocal cords. All fish sounds are produced through mechanical vibration of tissues or hard structures, which then transmit pressure waves into the surrounding water.
Most known mechanisms fall into three main categories:
stridulation (rubbing structures together)
hydrodynamic or skeletal clicks
Some species also combine multiple mechanisms.
This is probably the most widespread mechanism in fishes that produce tonal or humming sounds.
The swim bladder is a gas-filled organ normally used for buoyancy regulation. Because it is filled with gas, it is also very good at transmitting and amplifying vibrations, which makes it useful as a resonating structure.
In sound-producing species, specialized sonic muscles attach to the swim bladder wall. These muscles can contract extremely rapidly.
When the muscles contract repeatedly, they cause the swim bladder to vibrate like a drum membrane. The gas inside the bladder transmits those vibrations outward as sound waves.
Important details about this system:
Sonic muscles are often among the fastest contracting muscles in vertebrates.
Contraction rates can reach 100–200 contractions per second in some species.
The frequency of the muscle contractions largely determines the pitch of the sound.
In some fish the muscles attach directly to the swim bladder wall. In others they attach to nearby bones that then transmit vibration to the bladder.
The swim bladder itself often has species-specific shapes or internal structures that affect resonance, which means different fish species produce characteristic sounds.
Well studied examples include fishes in the family Sciaenidae (drums and croakers), where large spawning aggregations can produce very loud collective drumming sounds.
Stridulation is sound production through friction between hard body parts.
The term comes from studies of insects, but the mechanical principle is the same in fish.
A fish produces sound by moving two structures against each other so that repeated contact produces vibration. This vibration then travels through the body and into the water.
Common structures involved include:
pectoral fin spines rubbing against the shoulder girdle
pharyngeal teeth grinding together
specialized ridges on bones or fin rays
Catfish are a well-known example. Many species have pectoral fin spines with serrated edges. When the spine rotates in its socket, the serrations scrape against the pectoral girdle bones.
This produces a series of rapid clicks or squeaks.
The motion can be repeated quickly, producing a sustained rasping sound.
Other fish use pharyngeal teeth (teeth located in the throat rather than the jaw). When these teeth grind against each other or against bony plates, they can generate audible clicking or crunching sounds.
Stridulatory mechanisms are common in reef fishes and benthic fishes that have robust skeletal elements capable of producing frictional vibration.
Tendon plucking and skeletal vibration
In some fish, sound production involves rapid movement of bones or tendons that strike or vibrate against other structures.
One well studied example occurs in toadfishes (family Batrachoididae).
Toadfishes produce a distinctive humming call. In this system, sonic muscles contract rapidly and pull on tendons connected to the swim bladder.
The bladder vibrates in response, but the tendon tension and skeletal attachment points influence the vibration pattern, producing a sustained hum.
Some fish also produce sharp knocks or pulses when skeletal elements briefly collide during rapid movements.
These sounds are usually short-duration pulses rather than continuous tones.
Jaw snapping and rapid mouth movements
Another sound source in some fishes is rapid movement of the jaws or mouth structures.
the jaws snap shut quickly
mouthparts strike against rigid skeletal structures
These movements produce brief pressure pulses in the water.
In reef environments, some fish species generate audible clicking sounds through repeated jaw movements during social interactions.
In many cases the sound is actually a secondary mechanical consequence of rapid feeding or territorial movements rather than a structure evolved purely for sound production.
Resonance and sound amplification
Regardless of how the initial vibration is produced, the sound must be transmitted into the surrounding water.
Several anatomical features help with this:
the swim bladder acting as a resonator
body tissues conducting vibration
skeletal structures transmitting energy outward
Because water transmits sound very efficiently, even relatively small vibrations can travel significant distances.
In species with specialized sonic systems, the swim bladder often functions as a resonant amplifier, which increases sound intensity and allows the signal to propagate farther.
These mechanisms represent different evolutionary solutions to the same problem: creating vibrations that propagate efficiently through water as sound.
The diversity of these mechanisms is one of the reasons fish bioacoustics is such an interesting field of study.
