The secret language of electric fish

Last week's International Sawfish Day caught my attention for an unusual reason. Among the glossy posters circulating online, one image lingered — a sawfish gliding through greenish water, its long snout bristling with sensors. The caption read: "Seeing with electricity."

That single phrase jolted me back to my undergraduate days, when I first learnt that many fish — far beyond the famous electric eel — communicate, hunt, and navigate using electric fields. What began as curiosity in a classroom slowly turned into fascination. Over time, I discovered that beneath the rivers and estuaries of the tropics lies a world where light and sound fade, but electricity speaks.

If we could eavesdrop on this world, we would not hear splashes or songs — we would hear an orchestra of static beeps. Each pulse, each frequency, carries meaning: a hunt, a warning, a flirtation, a subtle shift in mood. Electric fish do not merely shock; they converse.

An African elephantnose fish sends out gentle pulses, mapping its muddy world through ripples of electricity.

The masters of current

Among the most iconic is the electric eel, South America's legendary powerhouse. Found in the turbid Amazon and Orinoco basins, it can unleash up to 600 volts — enough to stun prey or startle an unsuspecting researcher. Yet what is less known is that the eel also emits gentler, low-voltage pulses, using them to sense its surroundings or "scan" potential mates.

In Africa's rivers, a different lineage took the same evolutionary path. The electric catfish prowls the Nile and Congo systems, its entire skin studded with electrocytes — specialised cells that generate current. Unlike the eel, it relies on short, high-voltage bursts to ambush prey at close range.

Then there are the subtler artists of the electric world — the weakly electric fish, such as the elephantnose and the brown ghost knifefish. Their electricity is not a weapon but a language. They emit continuous, low-amplitude discharges that bounce off nearby objects, allowing them to construct an internal map of the muddy riverbed. Every ripple in the electric field tells them where a stone, plant, or insect lies — a living form of radar.

Back in the seas, the numbfish or torpedo rays roam coastal floors from the Indo-Pacific to the Atlantic. The name numbfish comes from the peculiar effect of their electric discharge — it can temporarily paralyse a human arm, leaving it numb and tingling. Local seamen and fishers have long known about this; some coastal communities even tell stories of "the stingray that shocks". Ancient Roman physicians once used these very shocks for pain relief, pressing live rays to aching joints.

Our ancestors may not have understood the science behind it, but they certainly knew its power.

A current through history

Electric fish did not just shape ecosystems; they electrified human imagination. In the 18th century, natural philosophers puzzled over how an animal could generate lightning within its body. One of them, Alessandro Volta, dissected electric eels and catfish, eventually building the first electric battery — the "Voltaic pile". The name still resonates every time we charge a phone.

Centuries later, engineers and neuroscientists continue to draw inspiration from these aquatic electricians. The eel's electrocytes, for example, inspired designs for bio-batteries that use chemical gradients instead of metals. Roboticists model autonomous underwater vehicles on weakly electric fish, giving them navigation systems that "feel" rather than see. Even brain–machine interface research borrows from the fish's ability to encode information in electrical patterns, helping to develop prosthetic limbs that respond more naturally to neural signals.

Evolution solved these problems millions of years before we wired our first circuits.

A black ghost knifefish glides like a ribbon of shadow, its body humming with electric pulses.

Conversations in the dark

If you were to swim among weakly electric fish at night, you wouldn't see them — but an electrode would reveal a vivid chatter of electrical voices. Each species, sometimes each individual, has its own frequency, its own signature pulse. When two signals overlap, one fish shifts its discharge slightly higher or lower to avoid interference — a behaviour known as the jamming avoidance response.

To an observer, it is like listening to polite radio stations adjusting frequencies so everyone can broadcast clearly. These pulses also serve as courtship songs. In knifefish, males can modulate the rhythm or amplitude of their signals to woo females, who recognise preferred frequencies. In their dark waters, electricity becomes both vision and voice.

The unseen senses of life

The electric sense — electroreception — is not confined to these specialists. Sharks, rays, and sawfish use similar organs called the ampullae of Lorenzini to detect the faint bioelectric fields of prey hidden in sand. Even some amphibians and mammals show primitive versions of this sense. Life, it seems, found electricity too useful to ignore.

Philosophically, this challenges our view of perception itself. We humans occupy a sensory niche dominated by light and sound. But for these fish, the world glows with invisible currents. Their Umwelt — a German term describing an organism's subjective sensory world — hums and flickers in ways we can't perceive.

What we call "silence" or "darkness" may simply be frequencies we fail to detect.

From rivers to revelations

In recent years, biologists have begun mapping the electric diversity of freshwater ecosystems — a kind of "electro-biodiversity". African rivers alone host over 200 species of weakly electric fish, each with its own waveform and behaviour. Studying these fish not only broadens taxonomy but also deepens our understanding of evolution and neurobiology.

For conservationists, they are also sentinels of freshwater health. Many species depend on clean, oxygen-rich water to generate consistent electric discharges. When pollution or sedimentation alters water chemistry, their electric language falters — a biological warning light for entire ecosystems.

A numbfish glides over the seabed — its electric organs ready to deliver a shock that can leave a human arm tingling.

Seeing the invisible

Every year, we lose species before we even learn their frequency — before we tune in to their silent songs. Electric fish, with their shimmering internal power, remind us that nature is layered with hidden dimensions.

Our own Bay of Bengal quietly shelters numbfishes, gliding unseen across the seabed. Local fishers know their shock well — yet no scientist has taken them up as a study subject. Perhaps it is time we looked into little things.

To truly understand life on Earth, perhaps we must first learn to sense the invisible — to listen, like a sawfish in the dark, to the quiet hum of existence flowing all around us.