Discards constitute one of the main problems with the world’s fisheries today, and are defined as all organic matter of animal origin retained by a fishing gear and thrown back into the sea, dead or with little chance of survival.
Discards may be fish of one or several untargeted species, but they may also be crustaceans, molluscs, marine mammals or seabirds.
The lack of regulations in the majority of fishing grounds causes a great part of the catch to be returned to the sea, as their marketing is prohibited or not commercially viable, are of a protected species, or juveniles too small to be landed, or they are under the legal minimum landing size or else the ship has already filled its fishing quota. In some cases, fish that are perfectly marketable are discarded to make room on the vessel for specimens that have a higher sales value, an unethical and wasteful practice known as highgrading. Highgrading is now illegal in various parts of the Baltic Sea.
The volume of discards is related to the quantity of unwanted species caught in fishing gear. The volume of by-catches in turn is influenced by various factors, such as the general state of the stock, if it is overfished a greater number of juveniles and other species will end up in the nets, or the type of fishing gear used, for instance beam trawls drag the seabed and bring in more by-catches than other gear.