Fish growing in isolated ponds?

[Pardel-Lux]

I posted a similar question in 2020, and the best answer, of course, was from Colibri, the late and much missed Curator of Critters:

How do fresh-water fish populate different basins?

Different kinds of freshwater fish have different levels of tolerance to salt water. What are known as “secondary freshwater fish” have some saltwater tolerance and can pass between mouths of separate rivers or cross narrow ocean barriers. Primary freshwater fish have little or no tolerance for saltwater and their dispersal is by other means. That may happen in a few species, but it is not the general means of dispersal of primary freshwater fish between different basins. In particular, this …