The Old World silversides are a family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

, Atherinidae, of fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 in the order Atheriniformes

Atheriniformes

Atheriniformes, also known as the silversides, is an order of ray-finned fish that includes the Old World silversides and several less-familiar families, including the unusual Phallostethidae...

. They occur worldwide in tropical and temperate waters. About two thirds of the species are marine, and the remainder live in fresh water.

Silversides are relatively small, with the largest species, the jacksmelt, Atherinopsis californiensis, reaching 44 centimetres (17.3 in), while most are under 20 centimetres (7.9 in), and several are not recorded at more than 5 centimetres (2 in).