How does an electric eels shock change if it were the size of a whale?

The problem I'm trying to elucidate is how a larger voltage from a much larger creature would change the range, power and duration of an electric shock. Another thing is if there will be any negative consequences to take into account, like if the voltage was simply too high and the creature would burn itself. Actually it's considered a mystery how they survive their own shock, so I guess I could handwave that part.

Electric eels are apparently not true eels but more closely related to catfish, which i've seen pictures of, they can grow absolutely massive! The idea is a species of Electric eel that swims in the open ocean and hunts in a somewhat similar manner to a blue whale, hunting mainly schools of small creatures. It would use its long body to circle around schools of fish or krill and shock them repeatedly before swallowing its incapacitated meal. There's also the possibility that sailors encounter the giant creature, and if they do how would let's say a cargo ship take a hit? What a about a plastic or wooden raft? Would there be bubbles on the surface due to electrolysis to serve as a possible warning sign?

An eels electric organs take about 80% of their body mass and they weigh 44 pounds (20 kilograms or so) and a blue whale weighs a whopping 130,000 to 150,000kg. For reference an eels discharge is about 600 volts.

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    $\begingroup$ "a mystery how they survive their own shock" their discharge lasts two milliseconds, not enough to cause damage to them. Their prey get stunned because they hunt animals that are much smaller. $\endgroup$ Commented Jul 29, 2021 at 10:57

2 Answers 2


Electric fish don't fry themselves because their discharge lasts no longer than three milliseconds. Source for the pulse duration: section III of this article about using electric eels to power lamps, because science! Seriously. Those guys even put this nice little graph about what they intend to do, I don't now why they didn't get the IgNobel in 2014:

Figure 11. Proposed scheme for energy harvesting from eels in a river, whichcomprises eels inside the baskets. All the output cables are connected to amanager circuit into a house, which carries out this power to be conditioned.Powering isolated areas is one of the most promising energetic utilizations forthe eels

Anyway, back to the topic at hand. Eels also don't fry themselves to death because while the voltage is high, the amperage is very low (for the eels). Prey gets stunned (or forced to move) because it is much smaller than the eels. It's like applying 45v to an adult man with gigantism and a toddler: one of them will shrug it off, the other will be quite jolted.

In eels the electrocytes are stacked along the length and the voltage is proportional to the length of the stack. Therefore, due to the Square-Cube law:

  • Voltage scales linearly with length;
  • But amperage will scale by the power of thirty two (25). $I=VenA$, where $I$ is the amperage, $V$ is voltage and $A$ is cross-section area. $e$ is the electron charge in Coulombs and $n$ is the amount of free electrons. Only the electron charge is constant here. Area scales quadratically and the amount of free electrons scales cubically.

Since the strength of the current grows so much faster than the body mass, at some point not far from the biggest size electric eels can attain in real life (~2.5m / 8ft) the animal starts frying its own nervous system when it discharges. A whale sized electric eel would be able to discharge exactly once in its life; it would form a few bubbles around itself from vaporized skin and innards escaping its body, but nothing impressive. It would then lifelessly sink to the bottom of the ocean.

Now, about this:

The idea is a species of Electric eel that swims in the open ocean.

Someone once asked Randall Munroe (the author of XKCD) about the feasibility to electrofish for whales. He had this to say:

So you want to give endangered whales powerful electric shocks. Great! I'm happy to help. This is definitely a very normal thing to want to do.

But he also said this:

(...) there's a catch: Most electrofishing is done in fresh water. Unfortunately, blue whales live in the ocean, where the salt water conducts electricity much more easily. That might seem like good news for our electrofishing plans, but it turns out to make it much more challenging.

Electrofishing works best when the water and the target animals are about equally conductive. In highly conductive saltwater, most of the current flows past the animals in the water rather than through them. This means that ocean electrofishing requires much more power.

In the article Munroe mentions that in order to shock a whale in the sea you'd need three orders of magnitude more power than if the whale were in a river. Your mega-eel's sacrifice might just do it, or it might turn a whole school of fish into unedible coal-like stuff. But in any way this is indicative that fish would have little evolutive pressure to evolve gigantic electric organs in the open seas.

If you want a natural, impressive weapon for underwater, consider what nature has already provided. There is poison, suckers with hooks, animals that swallow prey larger than them etc. I am personally terrified of the portuguese man'o'war, which can have venomous tentacles as long as 50m / 165ft!

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    $\begingroup$ +1 for an answer involving the "square-cube law" given your username! $\endgroup$
    – JonSG
    Commented Jul 29, 2021 at 14:20
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    $\begingroup$ Very useful textbook answer. Yet again science ruins a perfectly good story, not that it matters. Also +1 for the beautiful and informative drawing! $\endgroup$ Commented Jul 29, 2021 at 14:58
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    $\begingroup$ so what we need is a smaller electric whale inside the whales mouth that won't explode from square-cube electricity generation. This whale gets stuck out Alien-style to zap its food. or maybe just provide smaller electricity organs. $\endgroup$
    – IT Alex
    Commented Jul 29, 2021 at 15:22
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    $\begingroup$ @LiveInAmbeR which you can slave with just a little handwavier, have your electric whales evolve insulation so they don't shock themselves, if they are actually whales and don't have gills they can be completely insulated. there is already evidence ells have some minor biological electrical insulation. $\endgroup$
    – John
    Commented Jul 29, 2021 at 15:27
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    $\begingroup$ I can even see a hunting mechanism, normally schools of fish part around predators, staying close but far enough not get eaten. this predators could dive into the school shock the whole school then eat the stunned fish. $\endgroup$
    – John
    Commented Jul 29, 2021 at 15:30

One issue with this is that the energy output to shock a whole school of fish swarming in a cube of water that would be easily 100x100x100 meters if not more would likely require more energy than the eel could get from eating its prey.

The bigger the creature is, the more energy efficient it needs to be at hunting, especially in the resource poor open ocean.

If you really insist on the eel using electricity to kill, maybe consider it being a specialized apex predator: it gets close to a baleen whale, stabs it with a barb in its tail, and used that barb to deliver extremely short but powerful electric shock that instantly kills or at least stuns the whale without the need to electrify a cubic kilometer of water around it.

Basically, a whale-hunting eel with a taser.

Have the eel use electricity as miserly as most creatures use venom, for maximum deadliness and efficiency.


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