> That is the only possible explanation for how fish could have populated isolated mountain lakes

isn't that a common question?

"How do fish appear in landlocked lakes/ponds/etc"?

After digging a pond and letting it fill with rainwater/groundwater, fish appear. I don't think its because people carried them there.

(don't really know the common answer though)

An alternative vector: "cloud seeding" (https://www.theguardian.com/science/2004/sep/09/science.rese...)

Charles Fort collected numerous data for his famous "The Book of the Damned" https://en.wikipedia.org/wiki/The_Book_of_the_Damned