Anchovies grow to a maximum of 20 centimeters. Their back is blue-green; their flanks are gray with a silver-colored stripe. They eat zooplankton and algae. Anchovies reproduce in brackish water. They used to be found in massive amounts in the Zuiderzee and western Wadden Sea. The large schools were always accompanied by large numbers of porpoises. The species lost important spawning grounds when the Afsluitdijk (Causeway) was completed in 1932. Since around 1960, the anchovies have practically disappeared from the Wadden Sea. However, in 1993, this species was found spawning again in the Wadden Sea. This was an omen that they were returning, since they are being caught more often in the North Sea.