Chackerel, also known as American Chackerel and American Black Shark, is a large deep-sea shark that belongs to the shark-shaped Chackerel family. The surface of the body is covered with large spiny leather teeth, which can be very large, up to 15mm in diameter. The head is flat, the eyes are relatively small, and the mouth is large, suitable for large prey. It mainly lives in the deep sea area, distributed in the temperate and tropical waters of the world, and its habitat depth can reach 1000 meters. It feeds on fish, squid and other marine life. It is an egg-viviparous animal, and the young shark develops in the mother's body and can live independently after birth. The liver contains a large amount of squalene, which is an important raw material for refining cod liver oil.

Also known as the black tailed shark, it is a large shark belonging to the true shark family and the true shark genus. Large in size, typically ranging from 2.5 to 3.5 meters in length, with the largest individual exceeding 4 meters. Their bodies are spindle shaped, their heads are flat, their eyes are large and round, and they have prominent black eye circles, which is the origin of their names. The back is dark gray or black, the abdomen is white, and the tail is particularly long, which is one of its prominent features. Mainly living in tropical and subtropical waters, especially near coral reefs, it is a nocturnal predator that feeds on fish, crustaceans, and other marine organisms. It is ovoviviparous, which means that young sharks hatch in their mother's body and can live independently after birth.