Millions of tonnes of marine organisms are dumped back into the sea each year worldwide from fishing fleets, mainly for purely economic reasons. These include non commercial species (invertebrates, fish, birds, mammals, turtles, etc.), even those that are threatened and protected, and also commercial species (such as juveniles or adults once fishing quotas have been reached)

Unfortunately, discarded animals have very little chance of survival, meaning they are simply removed from the sea, often without having the chance to reproduce or to completely fulfill their role in the marine community. This practice also has other indirect negative impacts on the ecosystem: it benefits opportunistic predatory species (some bird species for example, that proliferate at the expense of many other species) and cause, when the level of rotting discards is large, serious problems for organisms living on the sea bottom.

This vast and unnecessary waste of living resources not only threatens the fate of marine ecosystems but also jeopardizes the future of fisheries.

The most recent global report (FAO, 2005) states that in the 1992-2001 period, 7.3 million tonnes of marine organisms were estimated to be discarded each year in the world, representing around 8% of the global catches.

Some fisheries have huge impact in terms of discards. Each year, the North Sea beam trawl fleets for sole, apart from destroying sea habitats, cause on average 330,000 tonnes of discards for 148,261 tonnes of landings. The discards problem looks even more dramatic when speaking about individuals instead of tonnes: European fleets targeting shrimps Crangon are reported to have discarded, in 1996, 928 million juvenile plaice, 16 million sole, 42 million cod and 55 million whiting, together with 75,000 million young shrimps annually.

Discards rates are highly variable. They depend on the type of fisheries (species targeted, fishing gear used, area or period, etc.). Some fisheries have totally unacceptable discards rates: the French deepwater trawl fisheries in western waters have discarded up to 90% of their catches. Nowadays, there are many of fisheries presenting alarming discards rates.