When a lake freezes, only the top layer actually freezes over. The area beneath the ice is where fish survive.
This is due to something called the anomalous expansion of water. Water becomes less dense and expands rather than contracts when the temperature goes from 104 degrees Fahrenheit to 32 degrees Fahrenheit. As a result, ice forms on top of the water, but not beneath it. Fish have no problem surviving a lake that is only iced over on the top of it.
- Seahorses are the only fish that swim upright.
- There are approximately 32,000 different kinds of fish known in the world today. This is more than all the other vertebrates combined.
- Sharks are the only fish that have eyelids.