All my big koi (6) died in Hurricane Isabel (we live in Virginia, along the
stretch where the storm hit the worst) . All the small ones survived.

(Big=15" Small = 3 to 6")

Two of them were dead by the morning after the storm, so I don't think it
was oxygen starvation. (They have survived much longer electrical outages with
no apparent stress. The two were dead after about 12 hours of no electricity.)
One or two large ones died every day after for 3 more days. All fish were top
breathing, however, including my normally bottom dwelling catfish. (The catfish
died later as well.) All smaller koi and my comets survived.

Two big trees fell w/in 30 feet of the pond. Could the 'boom' of the fall
created a shock wave that could kill fish in the same way that breaking ice
(that forms over a pond during the winter) with a hammer can?

Could the steady (but loud) drone of a generator do anything?

Why would only the big ones die?

Thanks for whatever information or "look here" sites that you can provide.
These were beautiful fish and I want to know if there is anything I could have
done to save them?

Roy