Eels are fish
165 comments
·September 3, 2025cl3misch
yndoendo
Recommend "The Truth About Animals" by Lucy Code [0]. It has good chapter on eels. They take a left and go to the USA or take a right and go to Europe.
[0] https://www.goodreads.com/book/show/34211802-the-unexpected-...
jemmyw
What about the ones in New Zealand and Australia? https://en.wikipedia.org/wiki/New_Zealand_longfin_eel
unwind
It's right there in the intro section:
Longfin eels are long-lived, migrating to the Pacific Ocean near Tonga to breed at the end of their lives. They are good climbers as juveniles and so are found in streams and lakes a long way inland.
weinzierl
I had the same thought. I always knew they were fish but always assumed they were local fresh water fish. I mean everyone talks about how Salmon does this incredible journey. If there was another species which did something equally incredible I should have heard about it.
Thanks for the link! A rabbit hole indeed.
kevin_thibedeau
These eels undergo a notable sequence of transformations before their journey back to the sea. It wasn't until the 19th century that science connected the transitions from glass eel (larval form), to elvers, to yellow eel (freshwater adult), to silver eel (ocean spawning) form as members of the same species. Salmon are less mysterious as their spawning could be observed.
ahoka
And Sigmund Freud spent some significant time researching Eel reproduction as it was a hot scientific topic at the time.
codr7
Eels are weird as fk, and much of what they're up to is still a mystery from what I understand.
j-krieger
I learnt this for my German fishing license. I was really baffled.
jansan
Of all the information in the Wikipedia article the fact that eels are fish was about the least interesting and only thing I previously knew.
ajnin
I'm surprised to learn that it is surprising that eels are fish. I mean, they live in water, they have fins, they're generally fish-shaped... What's more surprising is their incredible life cycle and reproductive journey. I'm surprised the author didn't put that in the title.
Vinnl
It's a brilliant title. I thought: huh, surely that's not a surprise? If that's a surprise, there must be more to eels than I know - which of course is what the article is actually about. If the title was just "eels have an interesting life cycle, actually", I probably wouldn't have realised how interesting it actually was.
yohbho
QI said (roll podcast title) There is no such thing as a fish, since that group is unbelievably diverse.
Strange that birds are dinosaurs, while Pterosaurs are not. Where is the bipedal fish that looks like a reptile or mamal, but is secretely a fish, too?
mutatio
I think it's not about diversity, but lineage. The phenotype for "fish" is so tight and well defined; a salmon is closer related to a human in the tree of life than to a coelacanth even though both are categorised as "fish".
Tagbert
I think you got that comparison backwards.
A coelacanth is a lobe-finned fish which is the group from which tetrapods, and thus humans, evolved.
A salmon is a ray-finned fish which is a very different group. These groups diverged sometime around 300MYA.
rzzzt
If not fish, why fish-shaped?
Joker_vD
Oh, but you should not classify living beings according to their habitat and behaviour; classification based on the degree of the phylogenetical relationship is obviously superior and the only truly reasonble one.
hatthew
You should classify living beings according to a system that is helpful to understand and discuss the livings beings in a given context. "Fish" isn't a specific taxon in the standard biological taxonomy, but is rather a description of a specific set of common physical attributes and behaviors that is helpful to differentiate some organisms from other organisms. Regardless of official taxonomy, for 99.99% of people it's helpful to describe eels as fish.
klipt
Phylogenetically, land vertebrates like us are fish too - we're descended from lobe finned fish.
So technically whales are fish, because all mammals are fish!
peanut-walrus
Of course whales are fish. Just look at them.
mkehrt
I can't tell if you are being facetious or not.
Joker_vD
I am; for a more serious take see [0].
Now, there’s something wrong with saying “whales are phylogenetically just as closely related to bass, herring, and salmon as these three are related to each other.” What’s wrong with the statement is that it’s false. But saying “whales are a kind of fish” isn’t.
null
adrian_b
The author does not appear to be aware of this but eels are not the most snake-like among fish.
Already the Ancient Greek and Roman authors had a classification of fish, where eels where less snake-like, because they have pectoral fins, while the most snake-like group of fishes consisted of morrays and lampreys, both of which have neither scales nor any kind of fins, being less similar to other fish than eels.
The loss of the legs and the elongation of the body, resulting in a snake-like form has happened not only in many groups of vertebrates, including eels and morrays, caecilian amphibians, snakes and several groups of legless lizards, but also in many worms, e.g. earthworms and leeches, which evolved from ancestors with legs. Even among mammals, weasels and their relatives have evolved towards a snake-like form, though they still have short legs.
jfengel
I know that the lampreys are often lumped in with the fish, but the jawed fish are more closely related to us than to lampreys.
(Fish aren't a clade at all so call em whatever you want.)
adrian_b
That is known today, but like I have said, the Ancient Greek and Roman authors, like Aristotle or Pliny the Elder, lumped together morrays and lampreys, because for some reason in the ancient world much more attention was paid to skin and limbs when classifying animals, than to the details of their jaws.
Because the Ancient Greeks and Romans used the same word for morrays and lampreys, when translating ancient texts it is difficult to decide which of the two was meant.
yohbho
morray seems to be muscian, you mean moray
dboreham
Wait what...Earthworms??
kevin_thibedeau
The directional bristles for anchoring to dirt (more noticeable on the larger earthworm species) are the remnants of polychaete parapodia. Similar to snakes that occasionally have remnant claws.
culturestate
Incredibly, I actually did learn this today because it was in the NYT crossword and I went down a very similar rabbit hole. I never made it to Freud, though, after I discovered and got sucked into the European Union Eel Regulation Framework[1].
If you, like me, are masochistically fascinated by this kind of “I can’t believe this is a real thing that the government actually does” documentation I recommend giving it a once-over.
1. https://oceans-and-fisheries.ec.europa.eu/ocean/marine-biodi...
jcattle
I mean, in this case who else should do it? If a fish in your local waters goes from relative abundance to critically endangered, who else but the government is supposed to step in?
culturestate
I don’t mean to suggest that governments shouldn’t do things like this, I’m just abnormally delighted when I find them.
A multinational framework explicitly for the protection and restoration of eels would never have occurred to me (or most of the rest of humanity, I’d imagine) but nevertheless it occurred to someone and now there are civil servants who are paid real money to design and implement it.
To put it another way, I’m less interested in the policy than I am in the mechanics of governance that enable it to exist. One of my favorites is the National Cemetary Administration Operational Standards and Measures[1] program, which basically defines OKRs for U.S. veterans cemeteries.
1. https://imlive.s3.amazonaws.com/Federal%20Government/ID25151...
athorax
Hank Green recently did a couple of videos on the topic
https://www.youtube.com/watch?v=On2V_L9jwS4
perihelions
Here's a long-form article on the same topic (the 19th century search for the spawning ground of eels)
https://www.newyorker.com/magazine/2020/05/25/where-do-eels-... ("Where Do Eels Come From?" (2020))
https://news.ycombinator.com/item?id=23265000 (56 comments)
Tzt
Well, there are also legless salamanders, that look like eels pretty much.
https://en.wikipedia.org/wiki/Two-toed_amphiuma
Some of them have no lungs even:
https://en.wikipedia.org/wiki/Microcaecilia_iwokramae
So, it makes sense to say that eels are fish, because there are lungless eel-like creatures that are actually amphibians.
flowerbreeze
There was a book about the eels being born from Sargasso sea, all transparent at first, that I remember reading ages ago. It mentioned a lot of legends as well surrounding the eels, because the young ones were never seen - only fully grown eels.
I cannot remember precisely, but to explain their existence, there were even some recipes about "creating" eels. I think one was something similar to "put a couple of sticks under a bit of wet turf for a night". And that is how the witches were able to create the eels.
I wish I could remember the title of the book, but unfortunately it was more than 30 years ago when I read it.
a_c
"The Book of Eels" touched a lot of topics you mentioned, not sure about the witch bit though. It was published in 2020 so probably not the one you are looking for. https://www.goodreads.com/book/show/51938590-the-book-of-eel...
rsynnott
> because the young ones were never seen - only fully grown eels.
Only, as it turns out, per the article the ones you normally see are _not_ fully grown eels; the sexually mature stage is also rarely seen.
truculent
Was it Waterland by Graham Swift (fiction, but has some eel diversions IIRC)?
agos
my favorite online newspaper recently did a long form piece on eels and their decline in Italy ([1] - Italian only, sorry).
The comments mention a couple of books:
- Brian M. Fagan, Fish on Friday
- Patrik Svensson, The Gospel of the Eels (also wrote another book on eels)
maybe it's one of these two!
flowerbreeze
Thank you! Since you mentioned the decline of eels book that was in Italian, I finally remembered the title too since it wasn't in English neither. It was this book in Estonian: https://www.goodreads.com/book/show/17609869-angerja-teekond.
The title translated to English would be something like "The Journey of Eel" by Aadu Hint. Published in 1950, so I'm rather certain it makes more sense to read the newer books these days.
s09dfhks
As someone whos allergic to fish, I ALSO learned eels are fish when we got some roasted eel as an appetizer and I had an anaphylaxis flare up :P
IAmBroom
I'm curious - are you allergic to both bony and cartiligenous fish?
NuclearPM
I don’t understand why you thought they weren’t fish. How is that possible?
maxglute
TFW random eel content popping up while i enjoy my unagi.
"We don't know where eels come from" https://www.youtube.com/watch?v=y0UIJekwyPY
jeffwass
I’ve learned all sorts of strange facts about eels by doing crossword puzzles. EEL is a super common crossword answer. If the clue references some aquatic creature and the answer is 3 letters long, very likely the answer is EEL.
amiga386
That's crosswordese for you - https://en.wikipedia.org/wiki/Crosswordese - there's also ERNEs, AUKs, TERNs and ORCAs out at sea
AndrewStephens
> out at sea
Surely you mean ASEA, my least favorite crossword non-word.
davmre
If you enjoyed this article then you must watch the A Capella Science music video on the same subject:
https://youtube.com/watch?v=TzN148WQ2OQ
By far the catchiest song about eel mating you will encounter today.
I read the blog post. Then I thought "surely the eels in my local southern German lakes can't be from the sea". But sure enough, the European eel hatches close to the Bahamas.
I audibly wtf'ed multiple times while going down this rabbit hole. Thanks!
https://en.wikipedia.org/wiki/European_eel