Hardhead Silverside

Atherinomorus stipes

The hardhead silverside is a small Caribbean baitfish that rarely exceeds 10 cm, with a broad head - the source of its name - a slender, near-transparent body and the bright silver flank stripe shared across the family. It is a Western Atlantic species, running from southern Florida and the Bahamas through the Yucatan and down to Brazil, with an isolated record from Tumaco on the Pacific coast of Colombia. It is unusually tolerant of changing salinity, turning up in fully marine water, in brackish lagoons and even in fresh water, and it associates readily with both coral reefs and open soft bottoms. For divers it is one of the defining sights of a shallow Caribbean reef: dense schools that hang in the surface layer above the reef crest and around mangrove edges, wheeling in unison until the whole mass flashes at once. Those schools feed on zooplankton and in turn feed almost everything larger, so tarpon, jacks, snapper and seabirds all work the bait balls - a swirl of diving birds overhead usually means silversides below. Fish mature at around 6 cm. The IUCN lists the species as Least Concern.