> I have the ANC breeding guidelines. Unfortunately if we were to follow
> those guidelines we'd need multiple people each devoting 10 tanks to
> each species. It would be nice but not even the ANC has found many
> (any) people willing to operate under their program rules. It was a
> nice idea, and would certainly maintain the viabilty if a large enough
> founding group was used. But resources are limited. Instead of keeping
> over 20 species I'd be down to just a couple species.
Hopefully we don't have any Africans on here or they may come after us
for our ANC breeding guidelines... :-) (sorry, couldn't resist going
after that typo)
The ACN breeding guidelines are actually very good. You also need to do
some reading between the lines and some improvisation. It was written to
represent the _best_ possible way of doing things. Has anyone on the list
actually read them other than Cary or I? I think that the thing with an
individual keeping 10 tanks for a given species is over the top for an
individual (but not an institution specializing in captive breeding).
Those ten tanks could easily be spread across a fish club as long as good
records are kept and fish get exchanged regularly. Imagine, if each club
takes on 10 species, and each species was only replicated by three other
clubs how many species could we maintain? Many, at least in the USA.
Personally though, I don't think many rainbows qualify for a conservation
orientated breeding program of this intensisty although again, there are
some exceptions to this of course.
FWIIW I have written a book review on the ACN guidelines. I can post it
if people think it worth doing so. Probably not as much use though if
one hasn't read the book.
> What I'd really like is feedback on which species can be maintained as
> linebred stock without problems and which must be outcrossed to other
> fish of the same strain to maintain viablity. There is also one other
> consideration, which species are actually hurt by out crossing? To go
I don't think anyone knows for 'bows or most fish. There are some things
that are postulated, but not really known.
> back to M pygmaea, now that there is a new captive population will it
> begin to suffer the same viablity problems as the early collection?
> Will crossing the two collections hurt the captive specimens or help
It may have been that just one of the parents had a rare flaw that
effected those offspring. The genetic characteristics of the founders is
very important and it is a matter of luck in getting all "normal" fish to
found a population from.
> it? I know there has been some discusion by folks working with
> threatened species that some species have very little heterzygosity in
> their gene pools and crossing them with the same species from other
> collections actually hurts the viability of the captive species.
I think here it depends upon if the crossing within the species is with
individuals from the same locality or different locality. Either way,
this is not likely to be outbreeding depression so much as a loss or
dilution of alleles in a population that may have allowed it to adapt to
local conditions (which sounds like the same thing as outbreeding
depression, and may be but I'll keep them separate just incase as I'm
not sure of the exact definitions genetically). If it is from the same
population it shouldn't matter
at all. If it is a different locality you may be outbreeding depression
or a dilution of locally adapted alleles. ie, some populations of trout
can survive higher temps than others. If you cross two pops, one from a
cool spot and one from a warm spot, even if
they are the same species or subspecies or whatever it is likely that
fewer fish in the warm population will tolerate as higher temperature (I
guess though it could be advantagous to the cold stream population if
temperature was likely to be limiting in any way). Over
many generations or a good drought some fish may survive and restore the
local adaptation if it hasn't been too diluted and the whole lot get killed.
> Basically you bring in bad genes to a stabilized population and the
> species suffers. I believe they term the condition out-breeding
> depression as opposed to inbreeding depression. Both can be a problem
> that could wipe out our captive populations.
Just on a technical point, it is not the genes that get brought in, it is
the alleles for a given gene. Genes don't get lost or formed so much,
alleles do. A gene is just the place in the DNA for a given character.
The alleles determine how that character is manifested. From memory
outbreeding depression is thought to be caused by the breaking up of
coevolved gene complexes, ie alleles on different genes evolve at the
same time, when both occur you get the highest fittness, however, when
only one or the other occurs you get reduced fitness. Over time, natural
selection works on this and presumably eventually fixes these alleles
together (ie each allele becomes homozygous) that are advantageous. When
you cross this individual with one that doesn't have the same alleles it
breaks up the advantageous association. Or at least that's how I think
it goes! :-) That was after all a very basic and simplified example of
a very complex thing and I probably messed some of it up.
Ooroo
Peter Unmack
(Roy Boys credentials right here too!) :-) Call 1-800-ROYBOYS for details.
:-)