Ichthyology is the study of fish. This includes the biology, classification and conservation of fish, as well as fish farming for food and commercial purposes.

An ichthyologist is a biologist who studies fish. They investigate things like the history, environment, reproductive habits and behaviour of various fish species.

A fish is a cold-blooded vertebrate that lives in water and breathes using special organs called gills. Vertebrates are animals with backbones. A fish has fins and scales on the body.