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  1. #1
    Join Date
    May 2004
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    Leeds
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    I read in the Times yesterday that almost all rainbows and about half of brown trout stocked in our waters are triploid( an extra X chromosome channels sexual energy into growth) or all female (female fish fed with testosterone which makes them pseudo male).

    When did this first start ? Is it harming our waters ? Is this partly the reason why rainbows don't spawn in the UK, apart from a few exceptions?

  2. #2
    MarkTheSpark Guest

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    Triploids have been around for 20 or more years, and was done for two reasons; first, so the 'black' cock rainbow was a thing of the past, and secondly because it meant any escapees are infertile.

    In less enlightened times, the release of rainbows led to the colonisation of the Derbyshire Derwent and a few other rivers. In Denmark, I believe, some of the rivers have a run of steelheads (rainbows that have fed at sea) every year, and quite healthy breeding populations.

    The problem with all alien species is that we have no idea of the long-term effect of having them around. Though for rainbows, it's a case of so far, so good.

  3. #3
    Evan Guest

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    Diploid and Triploid trout are genetically modified to grow huge and to be sterile.... GM is anything but new and a win win situation in this case.

    Though I'd personally rather they left the Brown trout alone - that way there is some additional benefit to stocking if they breed and establish a wild population.

  4. #4
    MarkTheSpark Guest

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    GM goes back to the monks cross-fertilising runner beans, Evan. In this case, the GM is done by heating the fertilised ova for a short time; those that don't die are generally triploid.

    But there's a slight difference between this and physically chopping up DNA and inserting it in the growing cells of other species, Evan so I hope you weren't inferring that because we've been triploiding trout for years makes it Ok to cross-breed sheep with scorpions...

  5. #5
    Evan Guest

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    With scorpions, no.

    But sheep interbred with some of Marilyn Monroe's DNA preserved in her nail clippings ?

    The entire Welsh nation would rejoice....


  6. #6
    MarkTheSpark Guest

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    It's already been done.


















    Charlotte Church, her name is....

  7. #7

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    Ooohh that sounds nice Evan..!!

  8. #8
    Join Date
    May 2004
    Location
    Leeds
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    629

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    Thank you for the advice.

    I'm still wondering though - if all female brown trout are stocked in our rivers, this must surely skew the natural balance between male and female brownies ? Does this mean that the ability to generate new generations of brown trout fry is reduced ?

  9. #9
    Evan Guest

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    There basically isn't a natural balance when it comes to trout stocks.... man made and man managed every inch of the way.

    There may be a few remote Scottish loughs and hillside burns with a native un-managed population but they are pretty few and far between I am afraid.

    I for one would always treasure a half pound wildie far far more than a six or more pound farmed dip or trip, but not enough people feel that way to make it a business proposition.

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