Hawaiian Flagtail, Kuhlia sandvicensis
During the day Hawaiian flagtail (locally known as Aholehole) huddle in schools around the top of reefs and along drop-offs where turbulent water creates bubbles hiding them from predators in and around the Hawaiian Islands. Young flagtails will form schools in the shallow water near sandy beaches, mouths of streams, tide pools, and brackish water (salt and fresh water combined). At night the fish will swim to deeper water to feed.
The Hawaiian flagtail has fairly large eyes in comparison with its head, which is slightly concave. The top part of the eye will reflect a reddish tint in a bright light. The body is compressed, plain silver in color with an olive or bronze tint along its back and a forked tail that has a dark marking on the end, giving it its name flagtail. Adult length of fish will reach 6 inches, with a body depth of 2.6 – 2.9 inches.
The Hawaiian flagtail has one dorsal fin (top fin) with 10 spines and 11 – 12 soft rays. It has one anal fin (bottom fin) with 3 spines and 11 – 12 soft rays. The pectoral fins (fin on each side by the gills) have no spines but have 13 – 15 soft rays. The pelvic fins (fin on each side behind the pectorals) contain no spines or soft rays.
Its Diet consists mainly of plankton, insects, algae, and smaller fish. It is also prey for larger predatory fish. They become very aggressive during feeding.
The males and females have the same markings so they cannot be distinguished between each other.
Image Credit: Bryan Harry for the National Park Service/Wikipedia