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Fp nigerianus sex ratio of fry (Read 1185 times)
Salvatore Coniglio
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Fp nigerianus sex ratio of fry
Apr 8th, 2017 at 12:25am
 
Hi everyone,

I started breeding Fundulopanchax nigerianus gardneri Makurdi several months ago. I am having great success in obtaining eggs and fry seem to be growing reasonably well.

However none of the fry so far seem to be males. The oldest batch are already 2.5 months old. They are under an inch in size but have almost no color. I am reading about how this species is notorious for having extremely skewed sex ratios.

Surprisingly, there is very little information on this in any of the literature for beginners. I choose this species since it was recommended for beginners. Anyone have any advice? Is it possible some are males but havent colored up yet?
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James Langan
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Re: Fp nigerianus sex ratio of fry
Reply #1 - Apr 8th, 2017 at 2:17pm
 
Salvatore

In some killifish species specifically louessense, I've had great success lower the water temperature 2-3 dgF, for males, I've had large male populations >85% @ 72-73dgF, when lowering the water temp to distinctly below 71 68-69 dgF, I reared a much larger >50% concentration of males.  Some believe as I that killifish have what know as crocodile syndrome, where eggs raised at temperatures produce the same sex, so they have less chance to interbreed with siblings.

To do this I placed my tanks nearer to my  basement floor to lower the temperature. Just something to try... Let us know how things work for you,

Jim Langan AKA, Webmaster
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Salvatore Coniglio
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Re: Fp nigerianus sex ratio of fry
Reply #2 - Apr 8th, 2017 at 2:35pm
 
James Langan wrote on Apr 8th, 2017 at 2:17pm:
Salvatore

In some killifish species specifically louessense, I've had great success lower the water temperature 2-3 dgF, for males, I've had large male populations >85% @ 72-73dgF, when lowering the water temp to distinctly below 71 68-69 dgF, I reared a much larger >50% concentration of males.  Some believe as I that killifish have what know as crocodile syndrome, where eggs raised at temperatures produce the same sex, so they have less chance to interbreed with siblings.

To do this I placed my tanks nearer to my  basement floor to lower the temperature. Just something to try... Let us know how things work for you,

Jim Langan AKA, Webmaster

Thanks Jim.

The temperature of all the tanks and egg trays is 72 F (room temp).

Could raising the temperature alter the ratio?

I can live with a skewed sex ratio, but having 100% females is undesireable. I also do not have experience as to when these fry are supposed to get their full color. It has been about 2.5 months. I am surprised how little information there is on raising fry there is in the literature.
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James Langan
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Re: Fp nigerianus sex ratio of fry
Reply #3 - Apr 9th, 2017 at 9:45am
 
Salvatore

One thing I forgot to mention is incubate my killi eggs in water tight containers inside the tank with the adults so the eggs incubate at the same temperature for development.  So the eggs are at a very stable temp, the are different publications on egg development temp and its likely that sex is determined during development not at fertilization.  I'll try to post some photos as to how I do this...

Keeping your temperatures 2-3 dgF apart will make a difference one way or the other

Good Luck, Jim Langan, AKA Webmaster
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Matt Kaufman
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Re: Fp nigerianus sex ratio of fry
Reply #4 - Apr 9th, 2017 at 2:47pm
 
One thing to ensure is that you keep track of each egg; many a time fry eat each other, so you pick 50 eggs, 20 hatch, 8 make it to juvenile of which 7 are males, ergo, skewed. Not necessarily. If you start with 50 eggs and end up with 50 juveniles that are 90% male, yes, that's skewed.

As Jim's pointed out, environmental factors can matter like temperature and pH. There's really  no one answer. Some fish are great - 50/50 with no effort. Most are skewed one way or another. There's no one-size-fits-all answer.

Another 'old time' trick I used once with a really skewed fish (A. ogo. ottogartneri) was raising eggs in pairs in ice cube trays and raising the fry separately. Ultra-tedious, but successful, got 50/50 mix. Anything beyond like 20 pairs was too much, though. I raised them in separate containers to adulthood, kept a few pairs of breeders that did yield better results in the offspring - still not 50/50 but more like 70/30 which was more suitable for breeding in big groups. Weirdly, after a few generations, the split went about 60/40 females. There were enough of us keeping that fish that we could swap males for females and we kept the line going for some time.

Some fish are really bad like Lamprichthys. 100% one sex is not uncommon. In fake lake Tanganyika water with careful attention to eggs and fry I could get about 1/3 females which kept me going. Some locals couldn't get females at all even starting with wild pairs.

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Salvatore Coniglio
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Re: Fp nigerianus sex ratio of fry
Reply #5 - Apr 17th, 2017 at 2:01pm
 
Still getting what seems to be only females (already 8 fish). They are beyond 3 months so I am assuming this is what they are.

I am going to try the ice cube tray method. Did you provide different water conditions in each partition?
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Matt Kaufman
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Re: Fp nigerianus sex ratio of fry
Reply #6 - Apr 18th, 2017 at 12:36am
 
No, raised all the fish in the same water.
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Matt Kaufman
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Re: Fp nigerianus sex ratio of fry
Reply #7 - Apr 18th, 2017 at 9:01am
 
One other thing. You can't really determine much from just 8 fish. Pick eggs every day for a week till you've got about 50, watch them for a few days and get rid of the fungused ones, then raise the remaining fry and then see. I'd do that before messing around with ice cube trays, it really is a pain.

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