Spratelloides delicatulus

Spratelloides delicatulus, the blue sprat, also known as the delicate round herring, blueback sprat, or piha, is a species of marineray-finned fish belonging to the familySpratelloididae,^[3][4] the small round herrings. This species has a wide Indo-Pacific distribution and has been recorded off Tel-Aviv on the Mediterranean coast of Israel.^[2]

Spratelloides delicatulus is a small, slender-bodied pelagic fish that typically reaches 5–7 cm in total length.^[4] The body is laterally compressed and silvery in color, often appearing translucent.^[4] Like other members of the order Clupeiformes, the species has a single dorsal fin and a forked caudal fin.^[5] The streamlined body shape and forked tail facilitate sustained swimming and schooling behavior in open coastal waters.^[5] Early descriptions distinguish the species from related taxa based on characteristics such as scale counts, fin placement, and proportional body measurements.^[5]

Spratelloides delicatulus occurs throughout the tropical Indo-Pacific region, including northern Australia, the Great Barrier Reef, Southeast Asia, and parts of the western Pacific.^[4] The species primarily inhabits shallow coastal waters and reef shelf environments.^[4] Populations occur both inshore and offshore across reef systems, with demographic variation observed across geographic regions.^[6]

Research on populations across the Great Barrier Reef shelf has shown differences in growth rates and reproductive timing between populations occurring at different latitudes.^[6] The species commonly forms large schools in nearshore waters where plankton productivity is high.^[6]

Spratelloides delicatulus feeds primarily on planktonic organisms in the water column.^[4] Observations have documented feeding aggregations during coral reef spawning events, including consumption of giant clam gametes.^[7] This opportunistic feeding behavior demonstrates the species’ role in reef nutrient cycling.^[7] The species also serves as an important prey item for larger predatory fishes and other marine predators.^[4]

Although Spratelloides delicatulus is not a major target of commercial fisheries, it is commonly used as baitfish in small-scale fisheries.^[4] Ecologically, the species occupies an important trophic position by linking plankton production to higher-level predators within reef ecosystems.^[6] Its abundance and short life cycle contribute to the stability of reef-associated food webs.^[6]