Why does my Dalmatian Mollie only have female Fry's?

Answer 1

I actually just learned this today, but the gender depends on the temp of your tank. I may be wrong but higher temps result in more females

Answer 2

I also considered the temperature factor, but couldn't find any sources to confirm it.

Another possibility is that both genders are produced, but only the females are surviving. In my experience (and my customers have verified this in their own tanks), when a water quality parameter begins to decline (and this would include temperatures that are "off"), male fish are the first to die. Why? I don't know - maybe because females have to be better able to withstand stress for egglaying/giving birth?

The only way you'll know this for certain is to be present at the birth and remove the female soon afterward and raise the fry to an age/size where they can be differentiated. If all survive and are female, try changing the temps next time! (For reptiles, mid-range temps produce both sexes if temps are a factor - high temps produce males). For mollies, the preferred temperature range is 70-82. Where does your tank temp fall?

Answer 3

I have bred fish as well as dogs. A lot of fish are born hermophrodite if thats the correct spelling lol. They are born female but for some reason can change at will to male when the time to breed comes along. In other words they are born with both sexual organs but only show the female ones.

Answer 4

Even though these fish are "born," it doesn't mean they have completed their development. Fry are too small to really be able to tell their gender. They may all well be female, but I would wait until they are fairly well-grown, at least to the size that they can be reintroduced to the adults, before making decisions about gender.

Answer 5

How old are the fry ? because most live fry look like females when young then they start to change as they get older

Answer 6

It sounds as though your pair may have a lethal sex-linked recessive gene; it's ok in the females, as they have another good copy of the female chromosome (analogous to the human X), but the it's being expressed in the males, who have no "spare" X, and it is killing them at some point before they are born.

Answer 7

I have heard that the pH of the water can be a deciding factor, with a low score producing more females.

Answer 8

I am a firm believer that temperature is a factor, but if they are all female a couple will definitely change to male.

Answer 9

You are lucky. We bought ours in Paris about 2 years ago and all we are getting are French fries.