Eli5: How do carp and other species get into lakes when they aren’t stocked?



So I’ve become a big freshwater fisherman in the past year or so. I’ve always wondered when I see the local lake records online how there are “smallmouth Buffalo” In a lake where only largemouth bass, catfish, and crappie have been stocked.

For example: https://tpwd.texas.gov/fishboat/fish/recreational/lakes/fayette/

This is a lake in Texas which has only been stocked with the fish I just mentioned.

How the hell did a small mouth Buffalo, carp, drum, gar or tilapia get into this power plant cooling reservoir?

Humans putting them there but not the fishing authorities? Flooding? I’m just spitballing here…

In: Other

Usually it’s birds, some fish eggs can pass through a birds digestive system unharmed, some stick to birds legs, feathers etc