> If Peter really thinks a lot of information on hybridisation between =
> various Rainbowfishes will convince the authorities to allow some =
> imports then I for one am willing to examine any proposal. IMO the =
> "hybridisation in the wild risk" is just a nice convenient peg on which =
> to hang the ban.
I think it is a legitamate threat. The biggest problem in some countries
is from translocation of related fishes and subsequent hybridization.
Sri Lanka is a classic case. I understand they don't have many exotic
species in the wild, but many natives have been moved and genomes have
been introgressed (ie hybridized). Trout have been screwed up everywhere
around the world that they are native. It's also happening to a degree
with suckers (catostomidae) in the western USA as they are being moved
around as bait and between basin water transfers. Go to Africa and try
and find a true Tilapia zilli genome. I'll bet you it's harder than you
imagine. We have potentially already screwed some things up in
Australia, but without decent beforehand genetic knowledge it may be hard
to tell. Murray-Darling stocks of golden perch were recently found to be
a different species to the Lake Eyre variety. I know MD fish have been
released into the Lake Eyre system and can still be released legally I
think. For the mean time I think anglers are the greatest threat through
stocking programs and bait transfers. I'm sure though aquarists will
play some role in there too as I know of people who have stocked farm
dams with fish from outside of their range and I'm sure people have had
ponds flood over (as has been reported early by Dr Ivantsoff) etc etc.
But, we start to go over old ground so I'll quit at that.
> We could never assemble enough data on this subject to =
> convince even a "little" sceptic (like Peter :-)) without trying to sway =
> a panel of beaurocrats/scientists who are hell-bent on protecting their =
> precious Salmonid feral fishery.
Part of the trick in that is not to do it yourself, but to have an
independant scientist type do the work themselves.
> . << It's just as easy to cross an albino with a normal type=20
> and spread around all these potentially recessive genes that you can't =
> see. =20
> Then you inbreed the population and before you know it all you have is=20
> recessives.>>=20
> I think that is a nice sweeping generalisation that you would love to =
> point out if someone else had posted it Peter.
Ok, let me justify what I have just said with an example, all beit
slightly extreme but possible none the less. Let's say a fish keeper had
the only stock of a given rainbow in Australia (which there are a few
cases of in recent years) or only a couple of people have it. An albino of
fish X appears in a batch. This fish is backcrossed and a pure albino is
created. A disaster occurs and the country is only left with two fish, a
normal type and albino type. Let's also presume the ablinism is
recessive. Through several generations of breeding it would be possible
to purge the albino allele and return to the wild type (although this
would take a lot of breeding and several generations to really be sure as
many fish will carry the recessive albino gene and you won't see it until
it meets another hidden albino allele). In all this line breeding to get
rid of the albino allele you also may lose a bunch of other alleles
too, thus reducing the genetic variation. Then, the fish goes extinct in
the wild. Thus, the species chances of long term survival in the wild
(if they could be reintroduced) would be more compramised than if it
still had all it's original variation. That is my point. It is an
unlikely situation but still possible, especially in a less popular
species (like M. eachamensis for example). Again, I'm not saying that we
shouldn't investigate an albino if one turns up. But, I do think that
it's existance compromises the longer term conservation of that species
in captivity and the wild if something however unlikely should happen to
it. This danger also increases if someone deliberately crosses an albino
type with a wild type and spreads the fish around widely. Then you may
really get a lot of recessive albino alleles drifting around hidden.
Cheers
Peter Unmack