“Mute as a fish”? Not at all: this is how these animals communicate with each other

There ability to communicate effectively between individuals of the same species, and between different species, plays a fundamental role in the life of all animals. Fish are no exception, communicating in very different ways and using, often simultaneously, chemical signals (like pheromones), electric And soundIn this article we will focus on the latter, going into more detail about the acoustic communication of various species of fish and its obstacles, often represented by the human activities at sea.

What are the communication mechanisms of fish?

Fish possess the greater variety Of sound mechanisms among all the vertebratesthe vast subphylum of animals characterized by a bony (or cartilaginous) skeleton and the presence of the spine, from which they take their name. They are over 800in fact, the fish species known for the sound production and this number is destined to grow over time. As happens with all other animal groups (in technical jargon, tax), the acoustic characteristics of the sounds emitted from the fish may vary based on species, gender, size and age, and a proposed classification to distinguish them refers to the morphological structures that animals use when they emit sounds to communicate with other individuals of the same species.

According to this division, the main group would be composed of fish that emit sounds through the repetitive contraction of the swim bladderthe organ through which animals control their buoyancy in water. A sort of tambourine, which works thanks to the presence of real sound muscles, which contract on the bladder and generate the sound. This category includes freshwater fish of the genus Pimelodus s., i Squirrel fish of the family Holocentridae, various species of piranha and of the family Doradae.

The second group of adaptations for sound production concerns the chest belti skeletal rays hey tendons which support the pectoral fins. For example, fish belonging to the family Cottoidea (which includes the bullhead, Gobio Cottusalso widespread in Northern and Central Italy) do not have a swim bladder, and emit sounds by making vibrate the chest beltcontracting a muscle that extends between it and the skull.
Not only that. Most of the catfishfamily Ictaluridaeemits a sort of buzz due to the rubbing of the rays of the pectoral fins, clearly audible even to the human ear. Another method of sound emission is the rubbing of special bony protrusions, called pharyngeal teeth, of the fish of the vast order of Perciformeswhich includes perch, remoras, angelfish and many others.
Finally, several studies are looking at the capacity that the gobies, family Gobiidaeto produce low-frequency sounds by means of the calibrated expulsion of water from the gill cover. We end this overview with the hypothesis, rather amusing and still under consideration by researchers, according to which the herring, Clupea harenguswould communicate with each other through a series of high-frequency pulses produced by the emission of air bubbles from the anal openingTalking farts, basically.

The difficulty of communicating in a noisy (aquatic) world

The noise produced by human activities in aquatic environments (and not only) it is, to all intents and purposes, a polluting agent. Think about the navigation of small and large vessels, offshore work, exploration and underwater energy production. Unfortunately, we would hardly be able to carry out all these functions without producing noise and numerous scientific studies demonstrate that, over time, this exerts a selective influence on the frequencies and methods used by animal species to communicate with each other. It should be remembered that fish did not evolve in a silent environment. Rivers, seas and oceans offer a whole set of sounds and noises, which those of you who love to dive to discover the seabed and tropical fish will know well. However, theevolution of sound mechanisms and their functioning occurred during a long period of timeof which we Homo sapiens we occupy a very small part.

Although scientific studies on effects of anthropogenic noise about fish are still few in number, today we know that some species, if too close to sources of noise, can die or be seriously injured. Similarly, it can happen that other species suffer a temporary reduction in hearing sensitivity or that the noise caused by the passage of ships and boats could reduce the effectiveness of communication interspecific. Imagine maintaining the same tone of voice that you would use in the library, during a big party, with the music at high volume: the quality of the information you give or receive would certainly suffer. The same thing happens to fish that, in the meantime, will continue to develop response behaviors or will learn to “raise your voice”as other sea inhabitants have already begun to do: the cetaceans. But that’s a story we’ll tell you next time.