system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can the same species of fish live in so many different lakes? Shouldn't we have more unique lakes with unique species as the lakes acts as closed enviroments?

And also, how does it even exist fish in really remote lakes that is far away from any nearby water?
gpt
Most lakes are *not* closed environments.  Salmon, for example, swim upstream and find their way into lakes, even if those lakes spill into the ocean and get their water from rain or snowmelt.  

Also, birds can carry eggs or seeds and plop them into other bodies of water.