> A question has came to mind about our populations of rainbows. Has
> anybody done any real testing on the amount of genetic diversity in
> different species of bows?
The folks at Queensland Uni have done some work. I don't know if that
has been published as yet though.
> It seems to me that any small isolated
> populations would by default become rather homogeneous in its genetic
> make up. But what about the other species. How long have we kept
> captive populations viable? Which species begin to fail if we don't
> outcross to other fish of the same strain? Or do strains go bad when
> we do outcross to others of the same strain but not from the same
> collection group? Seems to me, we really need to look into the answers
> to this for all the species we want to keep long term. In the states,
All these questions are largley unanswered and will probably remain so
for some time. Also, just because they are in captivity doesn't mean
they are going to become homozygous. The Lake Eacham 'bow is a good
example of a small captive population that still had reasonable variation
compared to other bows, although we still don't know how much was there
to begin with but it is likely to be comparable. Another potential
example is Goyder River tris. The recent wild collections look identical
to the first collections back in 1973 according to Neil Armstrong (if
maintanence of colour and shape means anything). Some folks report that
incisus and rubrostriate don't grow as quick as they used to or they have
higher infertility. I know we found that our survival rate of incisus
fry was not that brilliant. A batch of 100 would soon fizzle to 30
fish. I know some folks have problems getting larger number of fertile
eggs from G. wanamenisis. Now I don't know if there is a basis to these
observations, but through discussions like this maybe we can find a
pattern. Have people had trouble getting fertile eggs out of a given
species or had poor fry survival? These can be two characteristics that
begin to appear as a result of inbreeding but other factors could be
involved too. You also have to remember too that my discussion above is
limited to Australian examples. Some of the US fish may also fit this
scheme if they are from the same source of fish. Things like incisus
though I am sure have come from different sources.
Hooroo
Peter Unmack