What is fish scale?

Many fish have an outer covering of scales. Scales protect fish, much like a suit of armor. A fish scale is a tiny, hard plate that emerges from the fish's epidermis. Fish scales are made of bone from the dermal, or deeper, skin layer. Scales provide protection from the environment and from predators. They make swimming easier by minimising water friction and resistance.

These protective scales, which are also good camouflage due to reflection and coloration as well as potential hydrodynamic benefits, cover the skin of the majority of jawed fishes. Its first defense is to protect the fish's underlying structures such as nerves, blood vessels and bodily organs.

Fish scales are composed of a surface layer containing hydroxyapatite, calcium carbonate and a deeper layer made up of mostly collagen type I. Elements like Ca, Mg, P, Na, S are also present in minute concentrations.

Keratin, collagen, enamel, and protein-rich mucus make up the majority of fish scales. Collagen and mucus supply a significant amount of protein, particularly lysine. Calcium phosphate is abundant in fish scales, which provides as a calcium source for strong bones and teeth.

Collagen from such fish scales is often used in hydrolyzate form, i.e., protein hydrolyzate and collagen peptide. Such peptides are used in functional foods, as food additives and cosmetics applications due to their physical properties, tight structure and thermal stability.
What is fish scale?