The basket is in the pre-filter of my out of water pump that connects
to my bead filter. It's maybe...40' from the pond drain, so it's a
long ride with an abrupt end. The basket is very small for a large
fish. It's really intended for leaves and such, much like a swimming
pool pre-filter.

You can see it he
http://www.performancepropumps.com/Artesian.htm

I found another fish in there today, by the way. Roughly 6"x3"x1".
Alive, but its fins are a tattered mess like the last one I rescued.

It occurs to me that one solution would might be to have a larger, out
of pump, pre-filter. I'm pretty sure that it's the initial smash and
then the scraping about in the plastic strainer basket that's doing
the most damage, so If there was a separate larger, gentler, pre-
filter basket that they got deposited in, that would work well. Is
your pre-filter separate or part of the pump like this one? I'm
curious what's available out there...

The dead fish was definitely killed before it got to the basket. Based
on what's been coming through the line, it happened somewhere
else. : /