Latin name

Lateolabrax japonicus

Other name

Japanese seabass

Identification

The Japanese seabass has a slightly split tail and a large mouth with the lower jaw protruding beyond the upper jaw. 

Features of fish fins

It has 12 to 15 spines on the first dorsal fin and 12 to 14 soft rays on the second dorsal fin. The anal fin has 3 spines and 7 to 9 soft rays.

Fish colouring

Juveniles have small black spots on the back and dorsal fin that are usually lost in larger fish.

Distribution

Widespread in the western Pacific, where they are found from Japan to the South China Sea.

Habitat

Marine subtropical freshwater brackish, reef associated, catadromous species. Depth ranges from 5 to 100 meters. Japanese sea bass inhabit nearshore rocky reefs where there are currents. Juveniles have been recorded to ascend rivers and return to the sea as adults to spawn. 

Size

The maximum recorded total length is 102 centimeters (3.35 feet), although the more common standard length is 16.1 centimeters (6.3 inches), and the maximum published weight is 8.7 kilograms (19 pounds).

Behavior

In late winter or early spring, tidal currents disperse the juvenile fish and carry them miles from the spawning grounds to coastal areas and estuaries. Some of their habitats are around Japanese seas such as the Tamara River estuary, Tokyo Bay, Tango Sea, Ariake Bay, and Lake Shinji. Most of the early juvenile fish migrate to the zone of maximum turbidity upstream, which is known as an area of high prey concentration in estuaries. Juveniles that migrate to these areas have a better chance of survival than those that remain in coastal areas. The area of estuaries is smaller and environmental conditions are more variable, allowing for higher growth rates, less chance of starvation, and less risk of predation.

Food and feeding habits

The diet of early larvae consists exclusively of smaller zooplankton such as cyclopoids and paddlefish, with paddlefish being the dominant component of their diet, accounting for almost 70%. Once they reach the juvenile stage, their diet includes sardines, anchovies and shrimp, as well as all other small fish and crustaceans.

Reproduction

It is a protandrous hermaphrodite in which the males reach sexual maturity at about 2 years of age and turn into females when they are older. The larvae begin feeding on the 4th day after hatching. 

Spawning of this species occurs in coastal waters around Japan, especially in shelf areas with depths of less than 100 meters, between late October and late January. Generally, the eggs of Japanese sea bass are distributed between bays and outer waters as thermohaline areas are formed. However, once the eggs are formed, they move from the surface layer to the middle layer. The temperature of the water in which the eggs are placed is an important factor in survival, as the eggs cannot tolerate temperatures below 10°C. The eggs of this species are pelagic, spherical, colorless, 1.34 to 1.44 mm in diameter, with a single oil droplet. The transition from larval to juvenile stage occurs between 49 and 70 days of age, and the juvenile stage begins at 60 days of age.

Fishing

This species is commercially important, popular as a commercial fish, and farmed.

Relationship with a person

Harmless. Used in Chinese medicine.