Some common fish are catfish, sharks, salmon, trout and sturgeon.
To identify an animal as a fish, it should have these characteristics:
- Fish live in water.
- Fish have a backbone. They are vertebrates.
- Fish breathe using gills. They absorb oxygen through the gills.
- Almost all fish are cold-blooded. Two of the exceptions are the tuna and the Pacific salmon shark, which can raise their body temperature to some degree.
- Some fish have scales.