[ELi5] How do fish get in lakes/ponds when there is no inflow of water

Question

[ELi5] How do fish get in lakes/ponds when there is no inflow of water

In: Biology

Answer 1

1. Birds bringing eggs by accident
2. Huge Floods (e.g. like currently in Germany)
3. Lakes etc. separating over time, cutting off parts.
4. Seasonal changes, flooding etc.