Brackish Morays

[CFC]

I have come to the sad conclusion that the so called "freshwater" morays Gymnotorax tile should not be kept in home aquaria. My reasoning behind this is because we have just lost our largest eel to identical symptoms that we lost another large eel to 2 years ago.
A few days ago the largest of our G.tile eels started to behave strangly, swimming up in the water and being generally restless, we first put this down to the hot weather and the tank being unusually warm at 30c so i did a remedial water change and brought the temperature down slowly to a more acceptable 28c, this had no effect. Yesterday the eel started to show signs of swelling around the genital area, the same symptoms as our previous large eel showed before it died, and this morning the eel was in visable distress. Without much information to go on i made the decision to remove the fish to a freshwater quarentine tank working on the theory that she was most likely spawn bound and that they may spawn in freshwater since the young eels are collected from freshwater, this seemed to stop the suffering but within 3 hours she was dead.
On cutting the corpse open it seems my theory was correct as the swelling behind the genital opening was full of tiny sticky clear eggs.

I believe the hot weather triggered a spawning responce and she was desperate to reach freshwater in which to breed, when no freshwater could be reached something happened inside her and she was unable to offload the large ammount of eggs that had been released from the ovaries.

 

[demonmagus]

that's really sad, the fact she was trying to breed

 

[AMS]

Sorry for your loss CFC. Perhaps this could be pinned in the "Brackish Aquarium Resource Center" to help warn others Gymnotorax tile owners.

 

[kanzaris]

I am real sorry to hear about your eel. You are not having much luck lately. (Reading your post 28th June) Just glad you haven't given up.

Sabby

 

[nmonks]

Hello CFC,

I don't know much about moray eel reproduction, but a quick Google search turned up this nugget:

http/www.sheddaquarium.org/sea/fact_sheets.cfm?id=84

"Reproduction in moray eels begins with a courtship ritual in the summer months when the water is warmest."

Would seem to chime well with your observation. Having seen female halfbeaks die from not being able to give birth, I agree its a gruesome and obviously nasty way for any fish to die. Quite possibly these are fish that shouldn't be kept in aquaria at all.

Fishabse suggests your species is anadromous (breeding in freshwater) but that would be rather unusual, given that all known eels (morays and others) have leptocephalan larvae that spend time in the ocean plankton. Possibly they spawn in rivers but the larvae drift out to see, and then when metamorphosed, the elvers swim back into the rivers. That would be similar to what true eels do.

Cheers,

Neale