I presume you are talking about behavioural type traits here? By and
large I don't think anyone knows too much for sure on any given fish
species except possilby a well studied one such as trout. Behaviour
tends to be strongly influenced by both genes and environment. Different
behaviours are influenced differently by genes and environment and
different species will vary in influence for the same traits. The only
way to tell is to experiment by raising fish under different conditions
and to quantify differences. Something that aquarists would be well
suited to do but never have.
> captive populations are returned to their natural environment will they
> over a number of generations regain the genetic diversity lost in
> captive populations?
My understanding of genetic theory indicates that once a species loses
genetic diversity it isn't re-created. Most changes to an organism's
genome are negative and the few that are beneficial are usually lost
through random drift because they start off at such a low frequency in
the population. Aside from this is the fact that changes to the genome
are relatively rare and it would probably take 1000's of generations for
any new genetic variation to begin to appear.
Tootles
Peter