Re: NANFA-L-- Re: Chinese Sturgeon on AquaBid OFF topic
Sun, 14 May 2006 00:59:47 +0700

I am not sure if they use the same technique or the same strain, but
here they try to make something of chain farm like - you get fry from
the company, feed them with company's food, and when the fish grows to
suitable size the company is supposed to buy them back. The problem
is that with so many farms around the fish's meat price drop and the
company refuse to buy back, leaving farmers in the cold...
Fortunately [?] not all fish are sterile somehow, and some farmers can
pump out fry on their own and you can imagine the rest...


"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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