Shadefish, the only species of the genus Shadefish in the family Shadefish, is also known as the hemp lousefish, harbor fish, fine-scaled boyfish, and lousefish. It generally weighs up to 3 kilograms, and the largest individual can reach 13 kilograms. The body is fusiform, laterally compressed. The snout is bluntly rounded. Eyes large, fat eyelids thick completely cover the eyes, so the name masked fish. The mouth is small and toothless. Body covered with small round scales, caudal fin long, posterior margin y forked, caudal fin base with 2 large scales. The back is greenish, and the sides and belly are silvery white. Distributed in the Pacific Ocean and Indian Ocean coast, in the Chinese waters are distributed.

The masked marlin is a warm-water grouping fish. It usually inhabits the outer sea and swims to estuaries or near-shore waters during the reproductive period from April to May every year, and occasionally enters freshwater. It can also live in brackish water. It feeds on phytoplankton and stops feeding in winter. It carries 3 to 5.4 million eggs. The eggs are floating and spherical. The hatchlings grow quickly. The meat is delicious. It is easy to breed. Taiwan, China is rich in chum fry, the Philippines and Indonesia are widely used as pond fish.