Spratelloides delicatulus (Bennett, 1831)
(Blue-Backed Sprat, Blue Sprat)
These small elongate silvery fish are perhaps most easily recognized by their erratic swimming pattern, adopted while picking plankton from the water. They are seen over reefs, usually in moderately turbulent areas over walls. They are bluish above and silvery white below. There are two dark horizontal lines at the base of the tail, difficult to see in the field. To about 4 in., but usually smaller. Indo-Pacific. Photos:top: juveniles, Pupukea, O`ahu.; bottom, Lehua Rock, Ni`ihau.