Re: hybrid fish

[Shireen Gonzaga <whimbrel at comcast_net>]

> Date: Mon, 3 Jun 2002 13:52:10 -0400
> From: "Wayne Jones" <waj at mnsi_net>

> I have always thought that people who are willing to keep fish in
> captivity and yet are completely against hybidization are being a little
> hypocritical.

I don't cross-breed simply because I want to enjoy the beauty
of a creature that nature took millions/billions of years to
create. I hope that's not being hypocritical.  :-)  Hybrids don't
upset me, tho', as long as they're kept separate from the parent
stocks and/or not released into the wild.

> Keeping fish in captivity alters the genetic makeup of
> that fish population anyway.

I've got a stunning example of it at home. I maintain a batch
of Endler's Livebearers that are direct descendants of the
original stock caught by John Endler back in 1975 in
Laguna de Patos in Venezuela (the only known location for
this fish). That means they have no "guppy" genes mixed
in. All my males have colorful patterns with very little variation
from each other. Then, a very nice person in Miami, who
collected from the same location in the late 1990s, sent me
some of his fish. The difference was amazing! The variety of
patterns in the "almost wild" males really blew me away.

> Captive fish populations end up being
> selected for aquarium conditions whether it is desirable or not. It's
> not like after a 100 generations you will be able to return domestic
> fish to the wild.

That's something that concerns me about endangered native fish
captive breeding programs. But then, the conservation folks gotta
try anyway ... it's better than doing nothing at all. Such breeding
and reintroduction programs have to be very carefully done, by
professionals. It's definitely not a neat little project for amateur
fishkeepers, no matter how well-meaning they are.

> With hybrids it is the same thing only dramatically
> more so.

> I know it extremely problematic if one were to accidentally and
> unkowingly aquire a hybrid but it is not so difficult to avoid if you
> are careful about where one buys fish. I would say that any breeder that
> passes hybrids off as pure stock is committing fraud and is definately
> unethical

Well, it may not be that simple. The appearance of a hybrid
depends on the fish species and how they're bred, wouldn't it?
I'm no genetics expert, but I can just image the manipulation
possibilities. If someone were to breed several generations of
species A but slips a few species B fish (known to interbreed
with species A) in-between, the resulting hybrids after many
generations could closely resemble the dominant species (A).

> but individuals should be free to make up their own minds
> about the ethics of breeding fish for looks.

Yes. What you do in the privacy of your own aquarium is your business.  :-)

> Another thing that bugs me is the assertion that hybridization does not
> occur in the wild. It is very likely just a convenient argument against
> crossing fish.

Happens in the bird world, where species ranges overlap.
Blue Wing Warbler x Golden Wing Warbler = Brewsters Warbler
Black-capped x Carolina Chickadee
Bullocks Oriole x Baltimore Oriole
Mallard x Black Duck

> Of course it occurs in the wild. I am sure there is
> nothing about a glass enclosure that promotes interbreeding. Two fish
> trapped in a pond in the wild with nothing else to do are just as likely
> to look for ways to alleviate boredom as any other animal.

Finally! An answer to why some species cross-breed in the wild!
Boredom.   ;-)

> Naturally the
> offspring are unlikely to survive but on the rare occasions that the
> offspring are better adapted to their enviroment than the competition,
> they will survive and probably give taxinomist types one more mystery to
> scratch their heads over. Maybe it only happens once every 100 years or
> so but on the genetic timescale that is still a pretty short time.

And if a fair fraction of the hybrids are consistently able to breed
with each other, it creates the potential for a new species. That's
how speciation gets its start, right? Cool.

> Personally I don't allow hybridizations to occur in my tanks and I would
> destroy the offspring if it did happen. However, I just can't see how
> crossbreeding is ethically wrong.

Awww.... don't destroy them. Give 'em to a kid, or use them as feeders
to keep them in the food chain. Or send them to me. I've been thinking
of starting a shelter for wayward fishies.  :-)

Well, I'm off to cross my Ludwigia arcuata with a mysterious giant
Anubias. If it doesn't eat me alive, I'll offer it for sale to benefit the
defense fund.  ;-)

cheers,
    shireen


--
Shireen Gonzaga
Baltimore
whimbrel at comcast_net




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