One point of caution here. Many of the fish that you see in shops in
the US (and elsewhere no doubt) are wild fish. Unless you have bred
these species for 5 or more generations you are probably not going to see
much inbreeding depression. Plus it depends upon the species. Some can
deal with inbreeding better than others. Overall though, I think your
point is a good one. Wouldn't it be interesting to compare the genetic
diversity of some select species that have been maintained in captivity
for many generations vs those in the wild. This would be especially easy
in a country such as Australia where many species have been illegal
imports since the mid 80's thus have been "inbreeding" for over 10 years
(except the few illegal ones that get smuggled in). You could then
compare that to a country that does allow importation and also wild
populations.
> So (finally) this is my question: Why don't aquarists aim to generate a
> large number of genetically isolated lines (say 10-20) for each species? The
> goal of maintaining a single genetically isolated stock is much easier
> achieved by an individual aquarist or club than the goal of preserving all
> of the species diversity. If enough independent lines are maintained, most
> of the genetic diversity in the original stock (which, hopefully,is not one
> fish) can be maintained indefinitely, as long as the lines are NOT crossed.
Again, this will probably work better for some species than others.
Overall though, it is something that we should be trying. For species
that don't take inbreeding very well the lines would just have to be
regularly mixed. One of the problems with genetic theory is that one
cannot generalise across species. The only way to determine which
breeding strategy works best for a species is to breed them and examine
the results. Genetic theory should be used as starting point, but then
experience with a given species should prevail for that species.
Overall, some very good ideas for consideration.
Tootles
Peter