You've probably wondered at some point whether fish can communicate and how they do it. Several groups of scientists have explored this question and conducted research to demonstrate that fish can communicate with each other through various mechanisms.
In this article we will show you how fish can communicate, integrating what is already known from observation and experiments with recent findings from marine bioacoustics on acoustic, chemical and visual signals , their ecological utility and their relevance for conservation.
Communication sounds
Various studies have shown that fish also have the ability to communicate with each other; they do so with sounds similar to grunts and thumps , clicks, buzzes, or series of rhythmic pulses. In the aquatic environment, sound travels faster and attenuates less than in air, making it a very effective signal for exchanging information even in low visibility.
New Zealand scientists believe that all fish can hear, but not all have the ability to make sounds. Generally, species with a swim bladder connected to specialized, fast-twitching muscles that vibrate like a drum produce sounds; there are also species that generate sounds through stridulation (friction between bony or dental elements) or through hydrodynamic signals when changing speed or direction.
Professor Ghazali, from the University of Auckland, asserted that fish communicate when they need to scare off predators, when they are looking to mate , and when they need to orient themselves. This idea aligns with evidence that many species use sound for social cohesion , territorial defense , school coordination , and locating suitable habitats.
A clear example is the gurnard, which can make different sounds . One that remains silent is the cod, which only makes a sound when it needs to mate: " The hypothesis is that they use sound as a synchronization tool so that the male and female release their eggs at the same time, thus achieving successful fertilization ." Some reef-dwelling species generate noises to avoid being attacked by predators.
Goldfish seen in aquariums have excellent hearing , but they lack the ability to vocalize or make any sounds relevant to social communication, a good reminder that not all families have developed complex sound mechanisms.
- Why do they emit sounds? To attract a mate, mark territory, coordinate spawning, defend resources, request help, or warn of predators.
- How do they produce them? Vibration of the swim bladder by sonic muscles, friction of bones or teeth, and hydrodynamic signals.
- What advantages do they have? Greater range and speed than visual or chemical signals, and less dependence on water clarity and light.
Fish communication through urine
Another type of communication found in fish occurs through urine. Numerous studies have explored this phenomenon, including one published in the journal Behavioral Ecology and Sociobiology. This research indicates that fish can communicate through certain chemical substances in their urine , signaling internal states such as dominance , reproductive readiness, or readiness for aggression.
Communication plays a fundamental role in the life and development of fish. There are more territorial fish that have an aggressive behavior to be able to defend their land. In order to establish guidelines for marking the terrain, communication is needed.Studies suggest that chemical communication between fish plays a fundamental role in their coexistence. Although there are other clear signs that fish can communicate with each other, such as large schools. de peces, chemical communication is of vital importance.
Chemical signals include soluble compounds such as pheromones and nitrogenous metabolites that disperse rapidly. Although water dilutes and transports these substances, the aquatic environment is favorable for the transmission of chemical information over short and medium distances, especially in channels or shelters where the current is weaker.
Visual and acoustic signals have also been studied, combining with chemical signals to form a multimodal system . When it comes to urine, research attempts to determine whether fish use it to mark territory or to modulate the behavior of nearby rivals. The intensity, frequency, and context of urine emission appear to vary depending on the species and its ecology.
Urine experiment
To determine if urine played a role in territoriality, experiments were conducted in a water tank divided by a partition . Physical contact between the animals was avoided. The tank was designed so that the fish could see each other, but water from one compartment did not flow into the other. Fish of different sizes were placed in contact, as this is a key aspect for analyzing communication between rivals.
The fish were injected with a substance that dyed their urine blue so it could be measured and observed. Once this was done, the scientists began measuring how much urine the fish expelled in various situations. If several fish could see each other in the tank, they raised their fins and approached one another aggressively. They also excreted more urine compared to a situation where the two fish could not see each other.
Changes in the behavior patterns of fish that could see each other were also observed. These changes were only seen if the urine was transferred to the other side of the tank . In that case, if a fish saw a larger fish, it reduced its aggression and became more docile. This highlights the role of chemical signaling in fear of predation and territoriality. If the urine was unable to cross the septum, no change in behavior was observed, regardless of size.
This suggests that urine serves as a method of chemical communication among fish. It is possible to conclude that fish deliberately emit urine to communicate their motivational state and predisposition to aggression , and that this communication is tailored to the species, context, and time of year (migration, reproduction, or defense of a resource).
Communication method de peces: passive acoustics
Passive acoustics is a way to record and study how fish communicate using sound. Many species possess sound-producing organs : muscles that rhythmically tap on the swim bladder, or structures that creak through friction. It has been shown that most fish that can produce sounds have a swim bladder and/or bony elements adapted to vibrate or rub together. If you inflate a balloon and tap it, the effect is comparable to this internal "percussion."
In addition, fish can produce sounds by stridulating bony structures, moving tendons, or passing air through body cavities. These adaptations improve their survival in the aquatic environment: when attacked by a predator, a sound can unite the group and facilitate a coordinated escape.
The banks de peces They are very well organized and depend on the group for survival. In an emergency, communication—whether through acoustic, chemical, or visual signals— synchronize the responses and reduces reaction time to threats.
Technologies, sound libraries and their usefulness for preservation
Recent advances allow us to “listen” to the sea in great detail. Down-sea hydrophones , autonomous recorders, and spatial audio techniques combined with 360° video help identify which species produces each sound and in what context. These devices are deployed without direct human presence to avoid behavioral biases, capturing complete soundscapes over days or weeks.
Acoustic signals are already used to locate spawning aggregations , assess reef health, detect invasive species , and identify essential habitats. Some families are prominent producers of social sounds (such as Sciaenidae, Batrachoididae, and Pomacentridae), while others, like many cyprinids, are quieter. Even so, small species can be surprisingly loud relative to their size, with miniaturized vocal apparatuses that generate very intense signals for male competition or resource defense.
This information is organized into databases and sound libraries that bring together hundreds of recordings validated by specialists. Although the global catalog still covers a small fraction of the species de peces well-known, their continued growth facilitates comparative studies, training of recognition models and more precise fisheries management strategies.
One key aspect is that many sounds de peces are species-specific (or of a family), with differences in frequency, duration, and pulse patterns. This makes it possible to acoustic identification at a distance, as happens with birdsong, and opens the door to passive censuses in protected or remote areas without the need for continuous diving.
Ocean soundscapes and anthropogenic noise
The marine soundscape integrates three main components: geophony (abiotic noises, such as waves or rain), biophony (sounds) de peces and invertebrates, as well as marine mammals) and anthrophony (human activities). Understanding these components in each area allows for interpretation ecological patterns and detect anomalies.
Anthropogenic noise from maritime traffic, sonar, or acoustic deterrent devices can mask fish signals and cause physiological and behavioral effects: increased concealment, decreased reproduction , changes in feeding, increased stress , and even mortality in extreme cases. It's like trying to have a conversation amidst the din, which makes it difficult to attract a mate, coordinate spawning, or defend territory.
Understanding when, where, and how fish sound allows for the design of mitigation measures (noise-free zones, route regulations, schedules and speed limits, or fishing activity windows). This also helps to locate spawning areas for proper management, protecting critical moments in the life cycle.
- Non-invasive monitoring: Hydrophones record activity over long periods and detect daily, tidal, or lunar cycles.
- Fisheries management: The acoustic signature of spawning guides temporary closures and sustainable exploitation strategies.
- Restoration: Comparing the soundscape of healthy reefs with areas in recovery allows us to evaluate the success of the actions.
- Early detection: particular sounds make it easier to identify invasions or recolonizations without direct impact on the habitat.
Sounds have also begun to be documented in less studied groups, such as some cartilaginous fish, with recordings of intense chirps in interaction contexts. This reinforces the idea that the ocean's acoustic diversity is much greater than previously thought and that there is still ample room for exploration, especially in complex habitats like seagrass meadows or mangroves.
Beyond who "sings" and who doesn't, what's relevant is that fish use combinations of acoustic, chemical, and visual signals to solve challenges in their daily lives: finding a mate, defending a resource, or returning to their nighttime refuge. Together, these signals allow for surprising social coordination for such a diverse and ancient group of vertebrates.
With all of the above, the message is clear: fish are not mute; their world is full of sound and chemical messages that allow them to survive and thrive. From spawning grunts to chemical signals in urine or alarm clicks, each piece fits into a sophisticated language that science is deciphering thanks to passive acoustics , new recording technologies, and open sound libraries. As the catalog of recordings expands and human noise decreases, we will have better tools to conserve the species and ecosystems that depend on these underwater conversations.