Tony
"J. C." wrote:
>
> But with the tilapia(I have been looking into
> aquaculture for a few years), they used a process of
> GMO males being XYY instead of the normal XX or XY.
> When these male reds are bred to a female blue type
> the fish are XXY or XY. But they failed to take into
> account fish are not always subject to this law as
> other things determine sex such as pH, tempature,
> ect.. They found a way to reduce the number of fertile
> female by keeping the proper water chemistry and
> tempatures. The main reason for doing this is an all
> male batch of fish grow larger faster without the
> females distracting them for breeding. Females, being
> mouth brooders, stop eating for spawning and grow much
> slower in mixed populations. One site I read from
> South Africa told how to seperate the sexes for
> growing them seperately for better returns. This
> special red is available. And actually it is hard to
> get tilapia that has both sexes any more through the
> aquaculture sources. The number of fertile females
> from this process is only about 1/100. And the
> offspring of these females is still nearly all male. I
> doubt if these got loose in a tropical water way
> without normal tilapia that they could not keep
> reproducing and would die out in a few years.
>
> But it is hard to make those special males. Unlike
> where you breed a strain in captivity that can not
> make certain enzymes. These once made you can breed
> normally in captivity as long as you feed them with a
> diet rich in the enzyme they are missing. Those
> special male tilapia they make sell for $500 each. So
> that option is out for a wide spread distribution.
>
> Later, John
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