Do electric eels produce current as they just move about, and how/why?

Question

https://www.youtube.com/watch?v=y9wktSQdyaE

This video demonstrates how an electric eel can supposedly produce up to 800 watts, and power a Christmas tree, which is very topical (a late Merry Christmas to the Biology community!). The video, sadly, is not very detailed as to how this works.

I was under the impression that electrical discharge was a conscious action on the part of the eel, rather than a natural state for it. But, apparently, the electric eel generates electricity "whenever it moves," as the video's narrator put it? Do electric eels produce electricity subconsciously, just by moving? Surely, though the host lists off the 800 watts of power, it's not constantly producing 800 watts, either?

How do the fish's electrocytes work in this instance, where just lazing about is powering the Christmas tree?

Answer 1

You are right - the 800 Watts are not constantly produced:

There are three types of electrical discharge: (i) low voltage (ii) high voltage doublets or triplets and (iii) high voltage high frequency.

(i) low voltage allows the animal to orient itself in its environment [b].

(ii) high voltage doublets or triplets are used for hunting: By discharging a high voltage doublet or triplet the electric eel induces involuntary twitching in the prey animal. Since this twitching is producing a weak electric field, this allows the electric eel to locate its prey. See Figure 3 of [b].

(iii) high voltage high frequency is used to incapacitate the prey. It's about 400Hz at up to 600V [b]. Wikipedia [c] states that these electric eel can produce about 1Amp of current. That's in the region of 800Watts the narrator is speaking of. Edit2: The pulse duration is about 1ms [e]. With a frequency of 400-500Hz this leads to a surprisingly high ~50% dutycycle. The ability to keep the frequency stable depends on the age (=length) of your eel: The older the eel, the more stable the inter-pulse interval.
Caption: Fig3 from https://doi.org/10.3389/fnint.2019.00023, red=50cm, green=75cm, blue=115cm length of eel

In Figure 5 of [a] you can see that the electrical eel is able capture prey in ~5 sec. During these 5 seconds the electric eel is pretty much constantly producing high voltage discharges. These could be used to light a Christmas tree.

To summarize: Yes - electric eels are very much in control of when and how they discharge. This can be quite clearly seen (or rather heard) in [d] which is Supplementary Movie 8 from [a]

[a] https://www.nature.com/articles/ncomms9638

[b] https://s3.amazonaws.com/vu-wp0/wp-content/uploads/sites/182/2015/11/Science.pdf

[c] https://en.wikipedia.org/wiki/Electric_eel

[d] https://static-content.springer.com/esm/art%3A10.1038%2Fncomms9638/MediaObjects/41467_2015_BFncomms9638_MOESM559_ESM.mov

[e] https://www.frontiersin.org/articles/10.3389/fnint.2019.00023/full