The secret of the six antennae: How the catfish hunts with biological radar in murky water

By Vitali Dalke, fishing enthusiast and amateur biologist

A detailed analysis of the hunting strategy of Silurus glanis – sense of touch, taste and the art of trail tracking.

1. Introduction: The Catfish – The Ghost Hunter in the River

1.A. The evolutionary challenge of darkness

The European catfish, Silurus glanis , is the undisputed giant among the purely freshwater fish of Europe. It is a dominant predator and plays a crucial role in its ecosystems , which range from rivers to muddy lakes.
The catfish is a shadow hunter . It is predominantly active at night and at dusk, a behavior that makes it averse to light. During the day, he usually hides motionless in deep pits or under sunken trees. The real hunt begins in the dark. This nocturnal activity forces the catfish to track down prey when sight is impossible: in complete darkness or extremely murky water. To overcome this limitation, Silurus glanis uses a highly complex, multisensory system – it hunts using several senses simultaneously, which converge in its barbels.

1.B. The barbel as an evolutionary response

Barbels are more than just a distinguishing feature; they are highly specialized, flexible antennae . The European catfish possesses a total of six: two long barbels on the upper jaw (maxillary barbels) and four shorter barbels on the lower jaw (mandibular barbels). These "feelers" dramatically increase the sensory surface area of ​​the head, enabling the fish to continuously probe the substrate and surrounding water.

The barbels combine two vital senses that function independently of light:

1. Sense of touch ( mechanoreception )

2. Sense of taste ( chemoreception )

By combining these functions, the catfish can locate, identify, and track food sources even in complete darkness.

2. Anatomy of the antennae: Sensory structure of the barbels

2.A. Structure ( Morphology ) and Sensory Surface

The barbels serve as the primary interface to the environment. They are constantly in motion, scanning the bottom and the water column to receive signals. The surface of the barbels is a specialized layer of skin that contains a very high density of sensory structures.

2.B. The duality of sensors: Touch meets taste

The barbels are equipped with two types of sensors that simultaneously perceive mechanical and chemical stimuli:

1. Taste sensors ( chemoreceptors – the external tongue): The barbels are densely covered with taste buds and other chemical sensors. These structures allow the catfish to precisely detect dissolved chemical substances – especially amino acids and proteins released from live prey or carrion.
This works like an extension of the tongue and allows the identification of potential food via the chemical traces in the water.

2. Touch sensors ( mechanoreceptors ): Touch sensors are embedded in the skin layers to detect contact, pressure and vibration. This includes specialized sensory cells and, above all, free nerve endings .

Detailed examination of the touch sensors: The finesse of free nerve endings

Scientific studies emphasize the presence of free nerve endings . These often extend into the skin layers as a complex network of sensory nerve fibers ( myelinated and unmyelinated afferent fibers ). This structure suggests the enormous sensitivity and robustness of the Bartel's sense of touch.

Free nerve endings are often polymodal , meaning they respond not only to mechanical stimuli (pressure, vibration) but also potentially to temperature fluctuations or nonspecific chemical stimuli. These robust, general-purpose contact sensors enable the catfish to quickly trigger an alarm as soon as its barbels come into contact with objects. They form the basis for rapid, sensory localization and the response to unexpected touches.

3. Neurobiological circuits: Nerve supply ( innervation )

The efficiency of catfish barbels is based on a highly organized central processing of signals, which is controlled by specific cranial nerves.

3.A. The control of mechanosensors: The trigeminal system

The mechanical stimuli (touch, pressure) received via the barbels are primarily controlled and processed centrally via the trigeminal nerve ( nervus trigeminus – the fifth cranial nerve). This system transmits tactile information from the head to the brain.
The complexity of the processing is evident in the structure of the trigeminal nerve ganglion ( ganglion Gasseri ), which possesses a kind of spatial map ( somatotopic organization ) of sensory inputs. This specialized wiring is necessary to ensure precise spatial localization and mapping of the barbel contacts. Only in this way can the catfish determine the exact position of an object or prey in the immediate vicinity.

3.B. The coordination of chemoreception: vagus and trigeminal nerve interaction

Taste information ( gustatory information ) is processed by a cooperative system. The taste nerve cells on the barbels are supplied via both the trigeminal system and the vagus nerve ( CN X ).

Studies show a clear functional separation: The vagus system controls the actual intake of food or swallowing ( ingestion ). The barbels (via the trigeminal and vagus nerves) locate prey and identify it chemically. However, the final decision regarding food intake is made by the vagus nerve system.

This sensory hierarchy is an important protective mechanism: the barbels perform the rapid, exploratory detection work , while the critical decision as to whether the material is suitable is made by a separate vagal system. It has been demonstrated that there is no direct central connection between the barbelly taste system and the taste system in the mouth. This separate processing prevents the catfish, which often searches the muddy bottom, from accidentally ingesting unsuitable or harmful materials.

4.A. The precise weapon: The catfish as a current detector

When prey moves in dark or murky water, it leaves behind a signature of water vortices and changes in current that catfish can perfectly detect. Catfish hunting behavior is optimized to interpret these hydrodynamic disturbances . The barbels, in combination with the lateral line organ, are essential for the so-called wake-tracking method .

4.B. Mechanism and efficiency of wake tracking

Wake tracking is the ability to accurately track the water eddies and current disturbances created by swimming or fleeing prey over a distance and to reconstruct their movement patterns.

The efficiency of this system is remarkable. Experimental studies show that catfish can still trace the vortex trails of prey in the water several seconds later . This temporal accuracy ( temporal precision ), even in still water, testifies to the extraordinarily high sensitivity of the barbels' tactile sensors and the rapid decoding in the brain.

At the neuronal level, hunting information is encoded via the temporal sequence of present or absent nerve signals ( action potentials ). A stimulus, such as a pressure wave, triggers a specific sequence of signals. These are transmitted along nerve pathways to the brain and there decoded into precise environmental information – the position, speed, and direction of the prey.

Since the European catfish often prefer slow-flowing or still waters such as lakes. The hydrodynamic signatures remain intact there for longer. Its hunting strategy is perfectly adapted to the physical conditions of its primary habitats, maximizing its role as an apex predator.

4.C. Barteln as short-range sensors

While the lateral line organ plays a role in the perception of vibrations , the barbels function as near- field sensors . After the lateral system has determined the general direction of prey, the flexible barbels allow for fine-tuning and tactile probing in the immediate vicinity of the mouth. They are crucial for the precise localization and fixation of the prey before the final, powerful suction ( suction thrust or bite ). In the final moments of the attack, the barbels "feel" the prey in the spinal marks.

5. Integrating the multisensory image: The nighttime strategy

5.A. The cooperative hunting process

The catfish's hunting success is based on the seamless integration of its barbel senses. The fish performs a multisensory scan of its environment, combining distant tasting ( chemical detection ) with extremely precise near-field tactile perception ( mechanoreception and wake tracking).

Chemical perception ( chemoreception ) serves for initial identification: it helps the catfish to locate carrion or the approximate position of live prey via chemical traces. Tactile perception then fills the gap, especially when prey tries to avoid chemical traces. Wake tracking also allows the catfish to pursue fast, moving prey that is invisible in murky water.

5.B. The hypothesis of electrosensitivity

Besides touch and taste, there is scientific evidence suggesting that catfish (Siluriformes) may also possess the ability to perceive electric fields ( electrosensors ). This ability was already demonstrated in 1917 in the closely related catfish ( Ictalurus nebulosus ).

Although Silurus glanis itself still needs further research, research shows that catfish can be successfully trained ( conditioned ) to respond to electrical stimulation pulses. This implies that the perception of weak electric fields, which are generated by all living organisms, may be present. If the European catfish possesses electroreceptors, this would represent an additional, highly specialized method for detecting prey that is silently hiding on the bottom.

5.C. The optimal time window for hunting

The barbels' senses are the perfect tools for the catfish's main hunting season: dusk and night. The activity is strongly temperature-dependent, with maximum activity occurring in spring and late autumn. Catfish stop feeding when water temperatures drop below 4°C to 7°C . However, there are exceptions, such as a sudden rise in water temperature. I personally have caught catfish at 5°C.

Bodily functions ( physiological processes ) support this temperature pattern. The natural activity of nerve cells ( spontaneous firing rate ) increases with rising temperature. This suggests that sensory sensitivity and processing speed ( nerve cell activity [ neuronal activity ]) ) function optimally at higher water temperatures – i.e., in the warmer months.

6. Conclusion: The evolutionary excellence of the catfish

The barbels of the European catfish are a masterpiece of sensory integration. They are the primary evolutionary trait that enables Silurus glanis to fulfill its dominant role as an apex predator in the complex, often dark environment of various bodies of water.

The integrated system of chemical detection (taste) for food identification, tactile perception (touch) for contact, and sophisticated wake tracking for tracking movement demonstrates remarkable adaptability.

The catfish ( Silurus glanis) embodies the master class of non-visual hunting – a giant whose success is deeply rooted in the neurobiological provision of its flexible antennae, which has enabled it to make the night its preferred hunting time.