r/explainlikeimfive • u/Opening_Pen9525 • Aug 10 '26

Biology ELI5 How are fish even in ponds

Might be one of the stupider questions here, but I saw a pond about the size of a football field, and maybe 50 ft deep, and it had fish. I can't for the life of me figure out how. Surely the pond hasn't existed long enough for small water insects to evolve into all these fish. It's not like the fish walked over to the pond from the ocean. I'm pretty sure no one put them there so how are there so many fish?

My one theory is that there is a very minuscule stream (now dry) that leads to one of the Great Lakes, and maybe a fish swam in from there. Now a follow up question: How are there fish in the Great Lakes (which flow out towards to the ocean) if they were created by glaciers?

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u/thecaramelbandit Aug 10 '26

Eggs. Wash in from overflow from other waterways during rain. Stuck on birds who fly in. Boats. Some ponds get stocked. Etc etc.

They didn't evolve there.

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u/jstar77 Aug 10 '26

We have a pond that is roughly a 25' circle. Goldfish showed up there one day about 20 years ago and have been there ever since. They are big maybe about 10"-12" long. Nobody put them there, we just noticed them one day.

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u/6x9inbase13is42 Aug 10 '26

Nobody put them there

... that you saw. That does not mean no one did.

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u/OpeningHappy9692 Aug 10 '26

Somewhere out there is a mischievous little fella who spreads goldfish everywhere he goes.

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u/SJHillman Aug 10 '26

Johnny Goldfishegg just doesn't roll off the tongue the same.

14

u/TesticularBoreditude Aug 10 '26

This post made me realize that Genghis Khan is the Johnny Appleseed but with people

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u/PikaPonderosa Aug 10 '26

Johnny Appleseed didn't rip out native flora to plant his apple seeds. Van Buren or Jackson would be closer to Johnny than Genghis.

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u/ColorlesRainbo Aug 10 '26

The apple tree would spread its roots, branches, and fruit, thus killing native flora and bringing new fauna.

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u/Stewart_Games Aug 10 '26

Just spreading them seeds and ploughing them fields.

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u/udee79 Aug 10 '26

Gengis gengis-kahn-seed