Do fish fall down waterfalls a lot?

So I know a lot of fish like waterfalls and fastflowing rivers as hunting grounds. So naturally, both on top of a large waterfall as downstream, there's ususally a lot of fish activity.

Do fish on the top of a large waterfall know not to swim at the very end or do they fall down a lot? For large waterfalls, like 10 meter, this would definitely cause damage or death.