Anchovies are a family (Engraulidae) of small but common schooling saltwater plankton-feeding fish.  They are found in scattered areas throughout the world's oceans. Anchovies are concentrated in temperate waters, and are rare or absent in very cold or very warm seas.

Biology 

The anchovy is a small green fish with blue reflections. These reflections are due to a silver stripe that runs  along the length of the fish from the base of the caudal fin.  It is maximum  in length. The body shape is variable with more slender fish in northern populations.  The snout is blunt with small, sharp teeth in both jaws.  The mouth is larger than those of herrings and silversides, two fish which they closely resemble.  It eats plankton and fish larvae.

The Anchovy can tolerate  a wide range of temperatures and salinity. Large schools can be found in shallow, brackish areas with muddy bottoms, as in estuaries and bays.  

Spawning occurs between October and March, but not in water colder than 12 °C.  The anchovy appears to spawn 100 kilometers from the shore, near the surface of the water.

Habitat 
There are many Anchovies in the Mediterranean. They are regularly caught on the coasts of Sicily, Italy, France and Spain. The range of the species also extends along the Atlantic coast of Europe to the south of Norway.

As a food source 

The anchovy is a good food source for almost every predatory fish in its environment, including the California halibut, rock fish, yellowtail, sharks, chinook, and coho salmon.  It is also extremely important to marine mammals and birds; for example, California brown pelicans and elegant terns. The breeding success of these birds is strongly connected to anchovy abundance. As time progresses and the anchovy population drops, the population of the predatory species are also expected to decline. 

They are also eaten by humans.  Anchovies preserved by being gutted and salted in brine, matured, then packed in oil, are an important food fish, both popular and infamous for their strong flavor. In Roman times, they were the base for the fermented fish sauce called garum that was a staple of cuisine and an item of long-distance commerce produced in industrial quantities. Today they are a key ingredient in Caesar salad and Spaghetti alla Puttanesca, and are often used as a pizza topping. Because of the strong flavour they are also an ingredient in several sauces, including Worcestershire sauce and many fish sauces, and in some versions of Café de Paris butter.  They are most commonly marketed in small tins, either as "flat" filets, or as "rolled anchovies" where each fillet is rolled around a caper.  Both are quite salty. The flat fillets are usually more salty than the rolled anchovies.  They are also marketed in jars and tubes as a paste, mostly for use in making sauces, such as anchovy essence. Fishermen also use anchovies as bait for larger fish such as tuna and sea bass.  

The strong taste that people associate with anchovies is due to the curing process.  Fresh anchovies, known in Italy as alici, have a much softer and gentler flavor.  In English-speaking countries, alici are sometimes called "white anchovies", and are often served in a weak vinegar marinade.
This particular preservation method is associated with the coastal town of  Collioure in south east France. The white fillets (a little like marinated herrings) are sold in heavy salt, or the more popular garlic or tomato oil and vinegar marinade packs.

The European anchovy, Engraulis encrasicolus, is the anchovy of commerce. Morocco now leads the world in canned anchovies. The anchovy industry along the coast of Cantabria now dwarfs the traditional Catalan salters, though the industry was only started in Cantabria by Sicilian salters in the mid 19th century.

Setipinna taty or ikan bilis is the anchovy commonly used in South-East Asian cooking to make fish stock or sambals. Anchovy is also used to produce budu, by fermentation process.

Anchovies can concentrate domoic acid which causes amnesic shellfish poisoning.

Fishing 
Overfishing of anchovies has been a problem. Since the 1980s, large mechanized anchovy fishing vessels based in France have caught the fish in fine-mesh dragnets.

Spain beaching incident 
On September 29th, 2006, it was reported in the Associated Press that millions of anchovies with a weight of over three tons, had beached themselves in northern Spain, near Colunga, Asturias.  Tests on the dead fish did not detect any toxic chemical that could have caused the beaching, and the current working theory is that the school beached itself trying to escape from "hungry dolphins or tuna."  If the beached specimens had grown to maturity, it would have been more than "100 tons of potential breeders."

References 

Fisheries.vims.edu 
PSMFC.org

Clupeiformes
Teleosts