Sardines are silvery, laterally-flattened fish. They are members of the order Clupeiformes, commonly known as the herring order, and the suborder Clupeoidei. These fish usually live in warm marine waters, are found around the shores of every continent, and are an extremely valuable food fish.
There are four or five families in the order Clupeiformes. Two of the families are small: Denticipitidae contains only the denticle herring and Chirocentridae contains two species wolf herring. The third family, Engraulidae, contains various species of anchovies. The fourth family, the family Clupeidae, is the largest family in the order, containing sardines, true herrings, shads, and menhadens. Sardines are classified in three to five genera, the most common of which are Sardina, Sardinops, and Sardinella. These genera contain approximately 22 species. The fifth family in the order Clupeformes is Pristigasteridae and contains three genera, however its classification is under debate.
Sardines have a flat body which is covered with large, reflective, silvery scales. In the middle of their belly, they have a set of specialized scales, known as scutes, which are jagged and point backwards. Having very small teeth or no teeth at all, sardines eat plankton, which they filter from the water through their gills. While numerous species of sardines live off the coasts of India, China, Indonesia, and Japan, single sardine species dominate in areas like the English Channel and the California coast. Sardines are basically a warm-water fish, but occur as far north as Norway.
Schools, or shoals, of sardines swim near the water surface and are primarily marine, although some live in freshwater. Most species are migratory; in the Northern Hemisphere, for example, they migrate northward in the summer and southward in the winter. During spring and summer, they spawn. After doing this, the young commonly move closer to the shore to feed. The young sardines eat plant plankton (or phytoplankton), while adults eat animal plankton (zooplankton). All sardine species are important prey for larger fish.
The genus of true sardines, Sardina, contains only one species, Sardina pilchardus. Also referred to as pilchards, these sardines live off of the European coast in the Atlantic Ocean and in the Mediterranean and Black Seas. Their habitat is limited to areas where the temperature measures at or above 68°F (20°C). During the past 50 years, they have been found further and further northward, probably as a result of increases in global and seawater temperatures.
True sardines grow to about 10-12 in (25-30 cm) in body length. Their spawning period is rather long because of their wide distribution; in fact, depending on their location, fish of this species spawn almost continuously somewhere in their habitat. In the Northern Atlantic Ocean, these sardines migrate northward in the summer and southward in the fall to take advantage of better feeding opportunities.
The largest of the sardine genera, Sardinella, contains about 16 species, and fish from this genus are known by a variety of common names. For example, in the eastern United States, people refer to them as anchovies and Spanish sardines. In the southern Pacific, they are called oil or Indian sardines. These sardines inhabit the tropical parts of the Atlantic and Indian Oceans as well as the western portion of the Pacific Ocean. Sardinella aurita, the largest of all sardine species, is found in the Mediterranean and Black Seas and along the African coast. The majority offish in this genus grow no longer than 4-8 in (10-20 cm) long and have only limited commercial value as a food source.
The third genus, Sardinops, contains one species (Sardinops sagax ) that is known by a variety of common names. These are: blue pilchard, blue-bait, the Californian pilchard, the Pacific sardine, the Chilean sardine, the Japanese pilchard, the South African pilchard, and the Australian pilchard. They can grow to about 12 in (30 cm) long and, with the exception of the Australian pilchard, are very important commercially.
Sardinops sagax is known as the Pacific sardine along the coasts of eastern Asia and western North America. In North America, they are found from Baja California to British Columbia. Although this species spawns from January until June, most spawning occurs in March and April; and spawning occurs as far as 300 nautical miles away from shore.
Three or four days after spawning, the larvae hatch and make their way toward the coast; they measure about 3-5 in (7-12 cm). At this point, they are caught in large quantities by fishermen and used for bait to catch tuna. When they grow to about 7 in (17 cm), they leave the coast and meet the adults in the open sea. At two or three years old, they measure between 7-10 in (17-25 cm) and attain sexual maturity. These fish can live as long as 13 years. The population of this species is declining, probably because of overfishing.
Sardines are a very important source of food for many human populations. In fact, their importance is equal to that of the herring. People consume sardines in a variety of ways: dried, salted, smoked, or canned. People also use sardines for their oil and for meal.
See also Anchovy.
Moyle, Peter B. and Joseph J. Cech. Fishes: An Introduction to Ichthyology. 5th ed. New Jersey: Prentice Hall, 2003.
Nelson, Joseph S. Fishes of the World. New Jersey: John Wiley & Sons, Inc., 2006.
FishBase. “Sardinops sagax.” September 20, 2006. <http://filaman.ifm-geomar.de/Summary/SpeciesSummary.php?id=1477> (accessed November 27, 2006).
Kathryn D. Snavely