Bluelined Emperor

Gymnocranius grandoculis, commonly known as the blue-lined large-eye bream, iodine bream, Maori sea bream, or Robinson's sea bream, is a marine ray-finned fish in the family Lethrinidae, known for its wide distribution across the Indo-Pacific region.

Originally described under the name Cantharus grandoculis by French zoologist Achille Valenciennes in 1830 at the 🇸🇨 Seychelles, the species name "grandoculis" is derived from its notably large eyes, a distinctive characteristic of the species and its genus.

The species is characterized by an oblong body, with a body depth accommodating two and a half times its standard length. Adult specimens have a moderately sloping head profile, featuring a bony ridge on the nape and a bony shelf above the eye's anterior portion. The eye is positioned high on the head and is noticeably large, albeit slightly smaller than the snout. Its dorsal fin is continuous with 10 spines and 10 soft rays, while the anal fin comprises 2 spines and 10 soft rays. The jaws possess conical teeth at the front and a mix of bristle-like to conical teeth at the sides. The caudal fin is moderately forked, ending in pointed lobes. Gymnocranius grandoculis displays a golden brown to yellowish hue with wavy blue lines and spots on its head, cheek, and operculum. The fins are yellowish-orange, complemented by an orange margined caudal fin. The species frequently exhibits dark diagonal bars on its body and can grow to a maximum total length of 80 cm (31 in) and a weight of 5.5 kg (12 lb), with a more typical length of 64 cm (25 in).

This species is prevalent from the 🌊 Red Sea and 🇿🇦 South Africa across the 🌊 Indian Ocean to the Pacific, reaching north to 🇯🇵 Japan and east to the Tuamotu (🇵🇫 French Polynesia)s, extending south to 🇦🇺 Australia. In 🇦🇺 Australia, it is found from Yanchep in Western Australia to Townsville in Queensland, including the Cocos (Keeling) Islands and the Ashmore and Cartier Reefs in the Timor Sea. Gymnocranius grandoculis inhabits soft mud or sand substrates and rocky substrates in offshore waters, at depths of 50 to 100 m (160 to 330 ft).

Typically found either as solitary individuals or in small schools, Gymnocranius grandoculis primarily feeds on benthic invertebrates and smaller fish species.

This species is a significant target for artisanal fisheries throughout its range. It is chiefly caught using bottom longlines and trawls and is used as bait in tuna fisheries in the 🇵🇭 Philippines and is also taken as bycatch on the Great Barrier Reef.