bony fish – fish possessing a skeleton made of bone

To remember the meaning of bony fish, use the following mnemonic:

The thin and bony fish looked like a skeleton swimming around.

Bony fish are the largest and most diverse group of vertebrates, making up about 96% of all fish species and including most of the familiar fish we encounter. They are characterised by having a skeleton made primarily of bone rather than cartilage, which distinguishes them from cartilaginous fish like sharks and rays. Bony fish possess several key features including a swim bladder, a gas-filled organ that allows them to control their buoyancy and maintain their position in the water without constantly swimming, and a protective bony covering called an operculum that covers their gills and helps regulate water flow over the gill surfaces for efficient respiration. Their bodies are typically covered in overlapping scales that provide protection and reduce water resistance, and they have paired fins for manoeuvring and stability, along with a tail fin for propulsion. 

Bony fish exhibit incredible diversity in size, shape, habitat, and behaviour, ranging from tiny gobies just a few millimetres long to massive ocean sunfish weighing over 2000kg.