Shock Tactics

In the marine realm, animals employ a wide range of defensive weapons to ward off big predators: camouflage, mimicry, spines, spurs, toxins, venoms... But none is quite as striking and impressive as the electric organ discharge (or EOD) for short. A small number of so-called electric fishes are capable of producing an electric shock to see-off predators, or indeed, to take down their own prey. This includes several groups of rays and skates. So how on Earth does this work? How do these creatures generate electricity? How do they control it? And when do they use it?

Lesser electric rays use their electrical charges for communication and to ward off predators (Image Credit: RobertoCostaPinto / WikimediaCommons)

A Bolt from the Blue

There are very few species of fishes that can make electricity (Crampton, 2019).

"Electrogenesis" is not a common talent. There are just six groups of fishes that have independently evolved the ability to produce electrical currents. This makes up just 1.5% of all fish species (Crampton, 2019).

Electrical organs can be found in the elephant fishes (Family Mormyroidae) and the naked-back knifefishes and south American knifefishes (Order Gymnofrimes) aka the electric eels. These critters can produce an impressive 500 volts of shock (Crampton, 2019).

Within the sharks and rays, only skates (Order Rajiformes) and torpedo rays (Order Torpediniformes) are "electrogenic". This includes the infamous marbled electric ray (Torpedo marmorata), the numbfishes (Family Narcinidae) and sleeper rays (Family Narkidae) (Macesic & Kajiura, 2009; Crampton, 2019).

The marbled electric ray is capable of producing some 60 volts of electrical charge (Image Credit: Philippe Guillaume / WikimediaCommons)

Shell Shock

The electric batoids' electrogenic organs are paired and kidney-shaped; located on either side of their heads, in their pectoral fins. Within these specialised organs, electrical currents are generated in modified muscle cells called "electrocytes". The currents are produced when charged sodium atoms called "ions" are moved en masse across cell membranes to create a significant voltage differential - electricity. The arrangement of the electrocytes in columns acts like a row of batteries placed end-to-end; increasing the electrical output. So these organs effectively act like biological batteries (Macesic & Kajiura, 2009; Crampton, 2019; Papastamatiou et al, 2025).

Batoids have kidney-shaped electrogenesis organs in their pectoral fins. Only the lesser electric ray has an additional, smaller, spindle-shaped accessory electric organ(Image: Macesic & Kajiura, 2009).

This means that at will these critters can turn their entire body into an electrical source. In skates and electric rays, the charge is discharged out of their "dorsal side" (back), as this is the area of their body with the least resistance (Albert & Crampton, 2005; Papastamatiou et al, 2025).

Danger! High Voltage!

Skates and rays cannot produce as strong a shock as electric eels (some 400 volts), but that doesn't mean they don't still pack a punch! The electric organs of torpedo rays can have 45 to 70 columns of electrocytes acting like batteries, to put out some 60 volts of power. There are stories from fishers that have receive a nasty shock after handling these animals and this shock could even be enough to knock a human being unconscious! (Macesic & Kajiura, 2009; Crampton, 2019; Papastamatiou et al, 2025).

Skates produce a weaker, intermittent current (from around 1 mV to 1 volt). Yet their large electronic organs have many electrocytes connected in parallel, so their weak electric signals actually have a fairly broad range (Macesic & Kajiura, 2009; Crampton, 2019).

Culture Shock

The variations in charge strength in the different electric batoids is due to their contrasting applications. Not all these animals use their electricity in the same ways. For instance, skates use their weaker charge for communication (Macesic & Kajiura, 2009; Crampton, 2019).

Skates only produce a very small electrical charge compared to other electric fishes (Image Credit: LeGresley / WikimediaCommons)

Raja erinacea and Raja ocellata, more commonly known as the little skate and winter skate, are capable of producing electrical discharges that are unique to the species. The duration of the electrical pulse, the frequency and pattersn within the pulse vary between the species, so scientists suspect that their electrogenesis helps them to recognise members of their own kind (aka "conspecifics"), for the purposes of socialising and mating. Fascinatingly, their electrical pulses are not just unique to a species, but they can also be used to identify a specific individual. So it seems likely it plays a role in social communication (Bratton & Ayres, 1987; Crampton, 2019).

The lesser electric ray (Narcine brasiliensis) is an especially interesting example because their electrogenic organs are unique. As well as the main electrical organs and also spindle-shaped accessory electrical organs, that can produce weaker pulses. Scientists suspect that the more subtle charges are used for communication, whilst the stronger, main electric organs are used to create powerful shocks that ward off predators (Macesic & Kajiura, 2009).

Power Hungry

Another important function of electrogenesis is for foraging. Many species of skates and rays use their electrical charges to stun and subdue their prey. In these situations, they generate rapid vollies of strong, low-freqency discharges into their target (Macesic & Kajiura, 2009; Crampton, 2019).

Pacific electric rays change their electrical discharge depending on the context (Image Credit: Kathy Dewet-Oleson, NOAA / WikimediaCommons)

The Pacific electric ray (Torpedo californica), for example, discharges a strong shock when hunting their fish supper. They will jump over their prey whilst emitting hundred of repetitive trains of electrical impulses, that not only stuns, but can even kill. These rays can also tailor their discharges depending on the context. Their shocks are longer and more frequent during these predatory attacks than when employ their electricity for their own defence (Papastamatiou et al, 2025).

Electric torpedo rays, like this bullseye electric ray, are easy to identify thanks to the multiple, large fins down their tail (Image Credit: Steve Ray / WikimediaCommons)

Shock and Awe

Electric shocks can be a very effective defence. Electric rays housed in captivity have been witnessed discharging in order to repel away small sharks and crabs that were biting them. In the wild, this weapon can be used against large predators, like sharks and marine mammals (Papastamatiou et al, 2025).

When a Pacific electric ray is threatened by such an animal, they can discharge short, high rate electrical pulses in excess of 50 volts into their enemy. In contrast to the longer discharges they use for hunting, these short charges require a shorter recovery time, so they can be rapidly redeployed, in case the threat comes back  (Papastamatiou et al, 2025).

Pacific electric rays' discharges are so strong they can repel large predators, like great whites and tiger sharks (Image Credit: Laura Dts / Shutterstock)

And it seems this is a very effective defence. Scientists studying these electric rays in their natural habitats around Guadalupe Island, Mexico have observed that they are very bold; swimming in a very slow, relaxed manner, out in open, midwater areas, even around locations where large white sharks (Carcharodon carcharias), great hammerheads (Sphyrna mokkoran) and larger rays are known to frequent. Stomach contents analysis has shown that the electric rays are only very rarely a part of these big predators' diets (Papastamatiou et al, 2025).

Experts suspect that electric rays are confident because their electrical defences are especially effective on these large predators, as it disrupts their electrosensory systems, known as the ampullae of Lorenzini. To learn more about these amazing organs, head over to Sixth Sense. Strong electrical discharges into the predators would be overwhelming, unpleasant and even trigger involuntary muscle spasms; repelling the shark away, possibly without even ever making contact (Papastamatiou et al, 2025).

Skates, like this little skate, use their weak electrogenesis for social communication (Image Credit: Andy Martinez, NOAA / WikimediaCommons)

References

Albert JS & Crampton WG (2005). Electroreception and Electrogenesis. In:The physiology of fishes. Access online.

Bratton BO & Ayers JL (1987). Observations on the electric organ discharge of two skate species (Chondrichthyes: Rajidae) and its relationship to behaviour. Environmental Biology of fishes, 20:4. Access online.

Crampton WG (2019). Electroreception, electrogenesis and electric signal evolution. Journal of Fish Biology, 95. Access online.

Lowe CG, Bray RN & Nelson DR (1994). Feeding and associated electrical behavior of the Pacific electric ray Torpedo californica in the field. Marine Biology, 120. Access online.

Macesic LJ & Kajiura SM (2009). Electric organ morphology and function in the lesser electric ray, Narcine brasiliensis. Zoology, 112:6. Access online.

Papastamatiou YP, Luongo S, Ansaar A, Lowe CG & Hoyos‐Padilla M (2025). Electric rays defend themselves from large sharks using electric discharge. Ethology, e70005. Access online.