Tire Eel Breeding

[kcoleridge]

So I kinda have a weird story/question. In early May 2023, we purchased what was advertised as a zigzag eel from our local Pet Supermarket. We later found out it was a Tire Eel. We only ever had the one. It was in our 150 gallon tank with many different Cichlids, Catfish, and Barbs. It got really large really quickly, and it became aggressive about a month and a half ago and kept killing all the littler fish in the tank, even though we fed it very well. Anyways, so we wouldn't lose all the money we spent on our little fish, we took it to the local specialty aquarium store about 3 weeks ago to trade it in to someone who could keep it alone. Anyways we have just discovered over 3 weeks later, that we now have at least 2 tire track eel babies in our tank. Nothing we have read says that they breed in captivity, or that they are asexual, but here we are. It was a baby when we got it, we got rid of it 3 weeks ago, and now there are at least 2 babies in there. We may be the first people this has ever happened to, but we definitely have babies. Kinda crazy! Let me know your thoughts... not even sure where to post our experience since them breeding around other fish is so rare, much less one breeding alone... has this happened to anyone else or was ours just a special case? Thank you for reading!
-Kim and David

 

[tlindsey]

So I kinda have a weird story/question. In early May 2023, we purchased what was advertised as a zigzag eel from our local Pet Supermarket. We later found out it was a Tire Eel. We only ever had the one. It was in our 150 gallon tank with many different Cichlids, Catfish, and Barbs. It got really large really quickly, and it became aggressive about a month and a half ago and kept killing all the littler fish in the tank, even though we fed it very well. Anyways, so we wouldn't lose all the money we spent on our little fish, we took it to the local specialty aquarium store about 3 weeks ago to trade it in to someone who could keep it alone. Anyways we have just discovered over 3 weeks later, that we now have at least 2 tire track eel babies in our tank. Nothing we have read says that they breed in captivity, or that they are asexual, but here we are. It was a baby when we got it, we got rid of it 3 weeks ago, and now there are at least 2 babies in there. We may be the first people this has ever happened to, but we definitely have babies. Kinda crazy! Let me know your thoughts... not even sure where to post our experience since them breeding around other fish is so rare, much less one breeding alone... has this happened to anyone else or was ours just a special case? Thank you for reading!
-Kim and David

View attachment 1530366

Welcome aboard
First for me of hearing ofany breeding activity of any spiny eel species.

 

[Deadeye]

That’s crazy! How long did you have the first one?
Any chance some came in as hitchhikers?

 

[tlindsey]

Any chance some came in as hitchhikers?

I had the same thought as well. I was thinking eel larvae that couldn't be seen by the naked eye.

 

[kcoleridge]

I had the same thought as well. I was thinking eel larvae that couldn't be seen by the naked eye.

I am sure that is possible, but the only thing we got since then were just some ghost or feeder shrimp. What are the chances that there were two of the exact same species that hitchhiked? We are kinda in awe! Lol

 

[kcoleridge]

That’s crazy! How long did you have the first one?
Any chance some came in as hitchhikers?

We had the first one for about 5 months. It was definitely juvenile when we got it.

 

[tlindsey]

What

What are the chances that there were two of the exact same species that hitchhiked?

I would say zero

 

[LiquidUtopia]

Well I would think that you just got lucky. Obviously you have had a female and she was pregnant at the time. Either had eggs, or they live birth the babies. She was probably super aggressive because she was defending and looking after the young. All fish do it. I don't think breeding them is really that rare. They are too plentiful for aquarist not to be able to breed them. Without looking it up I would think live birth type but could be wrong. Could also be she gets fertilized internally and lays eggs. Again would need to research it. All the same very cool.

 

[LiquidUtopia]

Also wanted to mention. I have one as well. But, I beleive the one I ha very is of the mini variety. I've been very lucky with other than the fact it loves to enter my filter every so often looking for food I am assuming. They say they are super shy but I generally feed my fish by hand, literally will take blood worm and feed them from my fingers. The eel included will sit in my palm and take food from my fingers. Almost all my fish will do that now. I even use a plastic cup and let them swim inside it. Only reason I really do this is to make sure they all get some, it reduces uneaten food floating around the tank. Also it will alert me right away if someone's not feeling well.

 

[Fallen_Leaves16]

I heavily doubt it's possible- no mastacembelid is, as far as I'm aware, parthenogenetic to any extent, or able to retain sperm at all, certainly not at for months at a time, as they use external fertilisation to fertilise multiple hundreds of small eggs in a lengthy spawning ritual, not altogether dissimilar to what some cypriniformes do; furthermore, unless the fish was at least ~30cm SL at the time of acquirement, sexual maturity would not have even likely been reached at all. To date, I am not aware of any successful spawning attempt of a mastacembelid that did not involve hormone injections (and the vast majority of the scant number of successes was primarily work done with Macrognathus, a sister species to Mastacembelus); the many decades of rearing spiny eels in captivity should have, by rights, yielded a spawning report, had they been possible to breed without hormones in the home aquaria, no matter the difficulty (for there have been some dedicated efforts), but the lack of any concrete success is less than reassuring.
The few reports that do exist, however, all claim the fry to grow at a rate of about a centimetre per month under optimal conditions with plentiful food (and supposedly a large amount of high-protein foods are needed to keep mortality rates low); seeing as the fish in the picture you provided is just pushing five centimetres or so, I doubt it was a result of eggs from your original fish.
The body condition of the supposed offspring also raises a few doubts, but I don't think it'd be a reliable indicator of anything beyond anecdotal speculation.
Mastacembelids are not known to exhibit any sort of broodcare at all, and are in fact cannibalistic towards their young. Any aggression directed towards tankmates is merely territorialism or predatory behaviour.
Most likely theory, in my opinion, is that they were hitchhikers of some sort, which doesn't sound a very logical theory at all, but I can't really think of anything else that'd be plausible.