Sweeper
Sweepers are small, tropical marine ray-finned fish of the family Pempheridae. Found in the western Atlantic Ocean and Indo-Pacific region, the family contains about 80 species in two genera. One species is the target of subsistence fisheries in Japan, where the fish is much enjoyed for its taste. Sweepers are occasionally kept in marine aquaria.
Description
Deeply keeled, compressed bodies and large eyes typify sweepers, their form somewhat like hatchetfish; both cycloid and ctenoid scales may be present. The small, short dorsal fin begins before the body's midpoint and may have four to seven spines; the anal fin is extensive and usually has three spines. The mouth is subterminal and strongly oblique. Species of the genus Parapriacanthus have much more cylindrical bodies.Some species possess photophores. All but the curved sweeper possess a gas bladder. The largest species is the common bullseye at long; most other species measure or less. Colouration is relatively subdued.
Behaviour
Characteristically shallow water, schooling fish, sweepers are nocturnal and seek shelter under ledges or in the caves, nooks, and crannies of reefs or eroded, rocky shorelines during the day. They are often found sharing these hiding places with cardinalfishes and bigeyes, also nocturnal species. At night, sweepers forage for zooplankton, their primary food.At least one species, the small-scale bullseye of Australia, is known to enter coastal estuaries whilst young.