Fish sense sound waves from the water with their skin and muscles. Sound waves travel through the body hitting nerves in the ears which tell the brain when there is noise. Scientists can tell how old fish are from the otoliths, which are part of the inner ear. Gill covers protec the fragile and vital fish gills. They are composed of a few pieces of bone which very in shape and size depending on the species of fish.
Fish use it to detect any vibrations in the water.
This ability helps fish to stay tight in schools, detect predators and find food. The dorsal fin is located mid-way down the back. It acts as a keel for stability. These fins are located behind and below the gill covers. Along with several other fins, they are used for turning, backing up and motor movements.