How do fish get into pools in small streams high in the mountains, in
Australia? In many places I have seen fish living in pools that are up
waterfalls, sometimes more than 50 metres high - with so little water
flowing that I can't see how the fish could get up there. In many
cases, the pools do not connect to other pools, except at the height
of a one-in-ten-year flood, when the water would run incredibly fast.
So how do these fish get there and propegate?

This might be of interest:

http://www.wonderquest.com/fish-stock.htm

Oh they can swim up some waterfalls. I've seen salmon do it. They wait
till the rivers flood, and then swim upstream in the fast flowing
water. There are some fish that have sticky eggs that do stick onto
birds, also some of them have just been up high for a REALLY long
time. Some lakes have their own unique species, since they've been
landlocked for so long (Rift lakes in Africa). Humans also like to put
fish everywhere they can, you'd be surprised.

There are several ways the fish might have gotten inn amall streams
high in the mountains in Australia.

Firstly, the question can be answeed in a biological manner. The
introduction of non-native fishes into these areas is a common
practice in Australia and the rest of the world.  You can examine the
reduction of other animals due to this phenomena, ie. frogs.  To
better determine how a fish gets to the top, it would help to know
which fish you speak of.  Ie.  Mountain Galaxia undertakes a short
upstream migration to compensate for downstream displacement of larvae
& juveniles.


"Mountain Galaxias is very widespread in eastern Australia from sea
level to approximately 1800 m asl in inland and coastal rivers
draining the Great Dividing Range.  It occurs from southern Queensland
to eastern South Australia.  This species can be locally abundant
where trout are uncommon, otherwise populations tend to be sparse. 
Records in the Basin are from some Victorian tributaries including the
Broken and Ovens Rivers.  They prefer small mountain streams that are
well shaded and contain abundant cover from woody debris and
overhanging banks and vegetation."
http://www.mdbc.gov.au/subs/fish-info/native_info/mountainGalaxias.html

You can find more info on the Mountain Galaxia by doing in google search at:
://www.google.ca/search?q=Mountain+Galaxias+&btnG=Search&hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial


Although most fish are found by swimming there, there have always been
fish in these areas and can be related to the geographic history of
the location.  Lakes don't usually sit in isolation. There are rivers
or waterways in and out, and the fish can just swim to their new home
from their old one. But waterspouts have moved fish and fish eggs from
one place to another. Dry lakes can fill again with water, ie. rain or
flood, releasing fish and eggs that might have survived in muddy
patches.

Thanks for these great comments - thegreatgenius-ga gave me enough
leads that I believe I have my answer. Looking at pictures of the
Mountain Galaxias and Climbing Galaxias, I believe these may well be
the fish I have seen high in the mountains. These fish are able to
climb wet rocks and I imagine that they could, at times when it is
raining, scale the waterfalls and boulderfields needed to get into
these small pools in high mountain streams.

Thanks for the time people have taken to consider my question!