# Fish growing in isolated ponds?

**URL:** <https://boards.straightdope.com/t/fish-growing-in-isolated-ponds/979359>\
**Category:** In My Humble Opinion\
**Created:** [February 6, 2023, 2:37am UTC](https://boards.straightdope.com/t/fish-growing-in-isolated-ponds/979359 "2023-02-06T02:37:28Z")\
**Posts on this page:** 1\
**Showing post:** 16

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**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\
**Post date:** [February 6, 2023, 11:36pm UTC](https://boards.straightdope.com/t/fish-growing-in-isolated-ponds/979359/16 "2023-02-06T23:36:25Z")

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I posted a [similar question](https://boards.straightdope.com/t/how-do-fresh-water-fish-populate-different-basins/852117) 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?](https://boards.straightdope.com/t/how-do-fresh-water-fish-populate-different-basins/852117/7):
>
> Different kinds of freshwater fish have different levels of tolerance to salt water. What are known as [“secondary freshwater fish”](https://www.fishbase.de/glossary/Glossary.php?q=secondary+freshwater+fishes) have some saltwater tolerance and can pass between mouths of separate rivers or cross narrow ocean barriers. [Primary freshwater fish](https://www.fishbase.in/glossary/Glossary.php?q=primary+freshwater+fishes) 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 …

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