Knifefish Breeding

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dmed

dmed

Feeder Fish
MFK Member
Feb 8, 2008
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Cincinnati, Ohio, US
I find BGK very interesting and enjoy reading about them. However, I have never had any desire to breed them or to keep more than one at a time. I have read that all attempts at captive breeding of BGK have been unsuccessful. Of course, no one can know everything, so it's entirely possible that it has happened and I just haven't come across it yet. I haven't really put any energy into looking for ways that it could be done because it's not my desire, but I know that there are some people here and on other forums who really, really want to breed BGK.

I am fortunate enough to have the resources of a large university at my disposal and can access almost any textbook or scientific journal. Up to this point, I've said "researchers say you can't do it." If that is true, I'm hoping that maybe researchers can't breed BGK because they don't have the same desire and determination of someone who just really loves BGK.

I've decided that I will try to share information from journal articles that I have about breeding of other species of knife fish. I don't know if anyone wants the information or if it will be of any help, but I hope that someone will be able to put it to good use.

My real frustration has nothing to do with breeding fish, it's about the fact that anyone can type up a bunch of bunk and make it into a web page, then people will start quoting it like it's gospel. I'm not saying that there isn't any good information out there about breeding BGK, I'm just saying that there is definitely a whole lot of absolute crap circulating out there too. By my own criteria, you should not believe anything that I say either, so I will cite the sources in case someone wants to look up the actual article. I can't post entire articles because of copyright, but I will summarize the relevant information.

So, cheers :cheers: to anyone who is attempting to breed BGK in their home aquarium, and I really do wish you luck!
 
The first article I have about knife fish breeding in captivity describes the intentional, captive breeding of Eigenmannia virescens (glass knife fish) and Apteronotus leptorhynchus.

Hagedorn, M., Heiligenberg, W. "Court and spark: electric signals in the courtship and mating of gymnotoid fish." Animal Behavior, 33: 254-265.

The authors kept a total of 12 groups of fish in 200-800 liter (about 55-210 gallon) aquariums at temperatures ranging from 26-28C (78-82F). They were fed a high protein diet of chopped tubificid worms. Red lights were positioned over all the tanks to permit nighttime viewing. Because the two live in somewhat different habitats, E. virescens were provided with floating plants and A. leptorhynchus were given broken clay pots.

Each day, deionized water was added to the tank, enough to make the water level rise 1-5 cm. When the water got to the top of the tank, it was lowered by about 50%. Pumps on timers sprinkled water on the tops of the tanks for 3 hours every 6 hours. Within 8-12 weeks, this raised the resistivity (which is the opposite of conductivity) to 50-100 kOhm/cm. The room was temperature controlled, and the fish were kept on a 12 hour light/12 hour dark schedule.

The fish spawned as long as this "rain regime" was continued (anywhere from 10 weeks to over 6 months). E. veriscens pairs spawned 100 or more eggs in one night, and spawned again 4-7 days later, while A. leptorhynchus pairs spawned 5 to 30 eggs in one night. Neither species showed any caretaking activity over the eggs, and were observed to eat some of them. Both species spawned in plants, and in both species, eggs were fertilized in almost all cases by one dominant male in the tank.

E. veriscens fry hatched on the third day and the larvae fell to the bottom of the tank, they started to swim on the 7th to 8th day after spawning. Within another 2 days, their electric organs became active. A. leptorhynchus hatched after 2-3 days and began emitting electric discharge 8 days after spawning.

The research aspect of this article was to identify differences in the electrical discharge of the fish during spawning. Interstingly, E. virescens females will spawn eggs if a recording of a courting male's signals is played.
 
Those are interesting possibilities, and it's nice that a pet store "insider" can help find these sites. As I said, I'm out of the judgement business. Seems very probable in these particular situations. I hope they are doing it ethically.

Since these distributors don't say how they are breeding, I'm moving on to sharing whatever info I can find so hobbyists can give it a shot.
 
Quite possibly the same methods used with the farming of the polypterus species. They induce the spawning through hormones. A lot of the farmed bichirs have different patterns and other mutations including short body. I saw on a couple of lists there were also albino BGN and one they called blushing BGN where it was a faded coloration.
 
tezr;1945661; said:
Quite possibly the same methods used with the farming of the polypterus species. They induce the spawning through hormones. A lot of the farmed bichirs have different patterns and other mutations including short body. I saw on a couple of lists there were also albino BGN and one they called blushing BGN where it was a faded coloration.
Click to expand...

Yeah, that's what I meant by the "ethically" part. I haven't seen any information specifically about BGK, but for other knives it is known that some very particular conditions are required for the recrudescence of the gonads and for females to become gravid. It would be tempting for profit-minded large farms to manipulate the hormonal shifts artificially. I can't believe it would produce the best stock. That's why I'm hoping that a home aquarist can figure it out.
 
I know of two people breeding BGK's in Perth, Western Australia. Will try get some pics upof fry for you.

Has also been done over east to my knowledge. It has certainly been done many times before.
 
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