Blackside Hawkfish

The blackside hawkfish, also known as Paracirrhites forsteri or Forster's hawkfish, is a ray-finned fish belonging to the hawkfish family Cirrhitidae. Indigenous to the Indo-Pacific region, this species is occasionally found in the aquarium trade and has limited significance in local commercial fisheries. It typically grows up to 22 cm (9 in) in length.

First formally described in 1801 by the French naturalist Johann Gottlob Theaenus Schneider, the blackside hawkfish was originally given the scientific name Grammistes forsteri. The type locality is Vaitahu on Tahuata Island in the Marquesas Islands (🇵🇫 French Polynesia). The specific name is a tribute to the Polish-born German naturalist Johann Reinhold Forster, who was part of James Cook's second voyage on HMS Resolution and had referred to this species as "Perca taeniatus" in an unpublished manuscript.

The blackside hawkfish can reach a maximum total length of approximately 22 cm (9 in). Its dorsal fin consists of ten spines and eleven soft rays, while the anal fin is composed of three spines and six soft rays. The coloration of this species varies significantly among adults and during growth. Typically, the body is yellowish, with a prominent broad black or dark brown lateral band located mainly on the rear half. The head and front of the body are whitish or grey, adorned with red speckles. Juveniles in Asia may exhibit a reddish dorsal coloration, while those in Oceania tend to have golden-green upper parts and white underparts.

Native to the tropical and sub-tropical 🌊 Indo-Pacific Ocean, the blackside hawkfish can be found from East Africa and the 🌊 Red Sea to 🇯🇵 Japan, 🇳🇨 New Caledonia (🇫🇷 Overseas France), and Australasia. In 🇦🇺 Australia, its range extends from the northwest of Western Australia throughout the northern regions of the country, reaching the border of Queensland and New South Wales. It typically inhabits the seaward side of reefs and soft-bottomed lagoons at depths of 30 m (100 ft) and beyond.

As an ambush predator, the blackside hawkfish often waits on coral heads, supported by its rigid pectoral fins, ready to swiftly attack passing crustaceans or small fish. Although predominantly solitary, it may be observed in pairs or form small harems with one dominant male and multiple females. Similar to other members of its family, it is a sequential hermaphrodite. Initially, all individuals start as females, but the largest female in a group will change sex to become a male when the male's position becomes vacant.