Blue Sprat

Spratelloides robustus

The Rottnest Island herring (Spratelloides robustus), also known as the blue sprat, is a small herring in the family Clupeidae. Adults reach about 12 cm with a slender, streamlined body displaying a dark blue upper body and silvery lower body with a pair of horizontal dark blue streaks near the caudal fin. This species inhabits coastal waters around southern Australia from the Dampier Archipelago to southern Queensland, including Tasmania, at depths of 0-30 meters. They form enormous schooling aggregations numbering in the thousands near rocky reefs, jetties, and coastal structures. Blue sprats are planktivorous filter feeders consuming small crustaceans and phytoplankton. Their dense schools attract predators including larger fish, dolphins, and seabirds, creating dynamic feeding events. At Rottnest Island near Perth, large schools are a regular feature of dive sites.