Mackerel, like tuna fish, belong to the Scombridae family. They pertain to the open seas and are very agile swimmers. A special characteristic is that they do not have a swim bladder. A swim bladder ensures that the fish can adjust their weight to the water pressure and thus are able to float. Fish that live on the sea bed or are particularly fast swimmers (such as mackerel) have a regressed swim bladder or no swim bladder at all. This physical feature makes mackerel extremely mobile and helps them escape enemies such as the dogfish, porbeagle
(mackerel shark), tuna or dolphin. Mackerel have blue stripes on their back, usually reach a length of 50 centimetres and can live up to eleven years. It is a bright green-blue colour which turns to blue-silver after being caught. As with all fish of this genus five single small fins are behind both the second dorsal and anal fins. Due to the torpedo-like body shape it reaches remarkable speeds and can make a lightening-quick getaway, speedily seek greater depths or rapidly swim from the deep sea to the surface. The mackerel is a shoal fish and keeps mostly to the surface. In the winter rest period mackerel do not feed. In spring they feed on plankton and small crustaceans. In the late spring and summer after the spawning season their food demand increases rapidly. They hunt small fish in groups, especially young herring, sprat, cod, whiting and sand eel.
