Identification Characteristics:
The body is cylindrical, reaching a maximum length of 300mm. The upper section maintains a consistent width, while the lower section tapers towards the end of the body. Pigment granules are distributed throughout the body, concentrated along the midline of the dorsal and ventral surfaces. The head is smaller than the body. Tentacle formula is 3-4-21. The size of the suckers varies according to the tentacle formula. Suckers on the buccal lappets are irregular. The horny ring of the tentacle suckers usually has 8-15 conical teeth, evenly distributed over half the circumference of the ring. The tentacles have irregular teeth, randomly arranged around the horny ring. In males, the outer third of the fourth left tentacle transforms into a hectocotylus, with two rows of fleshy spines replacing the suckers.
Biology and Ecology:
Exhibits bioluminescence, the ability to change skin color, and secretes black ink that disperses in seawater to evade predators. This species is omnivorous, actively hunting prey, and typically rises to the surface at night to forage. Spawning occurs year-round, with peaks from February to May and August to October. Found in the open ocean, ranging from the surface to a depth of 170 meters.
Distribution:
Vietnam: Ha Long Bay (Quang Ninh), Do Son, Cat Ba, Bach Long Vy (Hai Phong); Nha Trang, Phan Rang, Phan Thiet, Vung Tau.
Global: Western Pacific Ocean, from the East and South China Sea to Japan, the Arafura Sea, and northwestern Australia to New South Wales.
Value:
The meat is palatable and highly valued for export and domestic consumption.
Status:
Subject to intensive exploitation, irrespective of size or season. The harvest yield is unstable.
Classification:
VU A1d.
Conservation Measures:
Included in the Vietnam Red Book (1992). Regulations on size and harvesting seasons are necessary. Further research on its biology and ecology is required for sustainable exploitation.