A sardine is a fish, although the common name is loosely applied to a variety of small, oily species. The term “sardine” acts as a commercial designation for several species of small forage fish within the herring suborder, Clupeoidei. This usage often leads to confusion because over 20 different species from multiple genera are marketed globally as sardines.
The Definitive Answer: Taxonomy and Scientific Classification
Sardines are classified within the Phylum Chordata, which includes all vertebrates. They belong to the Class Actinopterygii, meaning they are ray-finned fish, a group that represents the vast majority of bony fish species. This classification confirms they possess the fundamental characteristics of fish, including a backbone, gills for extracting oxygen, and fins for locomotion.
The scientific order for all sardine species is Clupeiformes, which also contains herrings and anchovies. Within this order, sardines belong to the Family Clupeidae, often referred to as the herring family. This family includes five main genera whose members are commonly called sardines, such as Sardina, Sardinops, and Sardinella.
Physical and Behavioral Characteristics
Sardines exhibit a small, elongated body structure adapted for swift movement in open water. Most species reach an average adult length of less than 12 inches, though the European pilchard can grow up to 27.5 centimeters. Their bodies are covered in large, thin, silvery scales, which help them camouflage by reflecting light.
These fish possess a single dorsal fin positioned near the midpoint of the body and a strongly forked tail, which provides thrust for rapid swimming. A primary behavioral trait of sardines is their tendency to form immense, dense aggregations known as schools. This schooling behavior is a defense mechanism against predators, as the sheer number of fish confuses attackers and increases individual survival chances. They feed primarily on plankton, which they filter from the water using specialized gill rakers.
Sardine vs. Pilchard: Understanding Regional Names
The confusion between the terms “sardine” and “pilchard” is purely a matter of regional and commercial nomenclature, not biological difference. In many parts of the world, particularly in European markets like the United Kingdom, the distinction is based on the size or age of the fish. Fish shorter than about 15 centimeters are called sardines, while the same species when larger and fully mature is marketed as a pilchard.
For example, a young Sardina pilchardus, the European species, is a sardine, but the adult is a pilchard. The name “sardine” has become a broad commercial term applied to numerous small, oily fish species from the Clupeidae family worldwide, often when packaged in cans. The international food standards organization recognizes that up to 21 different species can be legitimately labeled and sold as canned sardines.