Blackfin Dartfish

The Blackfin Dartfish (Ptereleotris evides) is a small marine fish found in tropical regions, primarily associated with coral reefs. It occupies a depth range of 1 to 30 meters (3 to 98 feet), but is most commonly found between 2 to 15 meters (6 to 49 feet). They can grow up to a maximum length of 14 cm (about 5.5 inches).

This species is characterized by its distinct coloration and markings. The body is light bluish-gray with darker shades toward the back. The snout is blackish, and the operculum, or gill cover, displays iridescent blue lines. The first dorsal fin is yellowish, while the second dorsal and anal fins are primarily blackish. The caudal fin has blackish to dark reddish lobes with a broad central area that appears whitish to yellowish. Juveniles have a notable black oval spot at the lower base of the caudal fin, which is larger than the eye.

The Blackfin Dartfish features seven dorsal spines, followed by 23 to 26 dorsal soft rays, one anal spine, and 23 to 26 anal soft rays. It has 26 vertebrae. These fish are often seen hovering 1 to 2 meters (3 to 6.5 feet) above the seabed, feeding on zooplankton.

They are usually found in pairs as adults, exhibiting monogamous behavior, while juveniles form small groups. This fish is generally observed swimming in the outer slopes of coral reefs, lagoons, and bays. When threatened, it prefers to swim away rather than hide in a burrow.

The Blackfin Dartfish has a wide distribution across the Indo-Pacific region, ranging from the 🌊 Red Sea and East Africa to the Line and Society Islands (🇵🇫 French Polynesia), extending north to 🇯🇵 Japan's Ryukyu and Ogasawara Islands, and south to New South Wales, Lord Howe Island, and Rapa. The genus name, Ptereleotris, is derived from the Greek words "pteron," meaning wing or fin, and "eleotris," a name for a Nile fish, which reflects their graceful and streamlined appearance.