F is for ... fish!
So how do fish get in lakes?
Even if lakes are isolated now they may not have been in the past, and fish could have entered them then.
Fertilised fish eggs can also be picked up by birds, and can be moved from river to lake.
And fish can even rain from the skies!
That's right - fish eggs or spratt (baby fish) can be sucked up in water spouts or tornadoes and transported many miles, raining down wherever the weather takes them!!!