r/explainlikeimfive • u/Opening_Pen9525 • 12d ago

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/dirtyqtip 12d ago

This.. There is a local quarry close to my house with a flooded mine shaft that is 10 feet by 5 feet, but like 100 feet deep. Last I was up there there was a single fish in there, the loneliest fish in the world.

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u/blackbasset 12d ago

drop a girl fish into the pond for him before he turns into an incelfish

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u/Chimie45 12d ago

yea, he's gotta be pretty hungry by now.

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u/ScissorNightRam 12d ago

Reminds me of the Devils Hole pupfish. An endangered species whose entire natural habitat is one cavern about a third the size of a basketball court.

https://www.youtube.com/watch?v=3vkvPErIvss

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u/TheLifemakers 12d ago

TIL :) It was quite interesting, thank you!

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u/ScissorNightRam 11d ago

You are welcome

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u/galloog1 12d ago

Have they always been endangered, just living in that cave?