Fishing at rates that exceed the sustained-yield cropping of fish species, resulting in a net population decline. For example, in the North Atlantic, herring has been fished to the verge of extinction, and the cod and haddock populations are severely depleted. In the developing world, use of huge factory ships, often by fisheries from industrialized countries, has depleted stocks for local communities who depend on this food source. In 2005, the Food and Agriculture Organization of the United Nations estimated that 52% of the world's marine stocks were fully exploited, 16% over-exploited, and 7% depleted. See also fishing and fisheries.
Environmentalists have long been concerned at the wider implications of overfishing, in particular the devastation wrought on oceanic food chains. The United Nations Food and Agriculture Organization estimates that worldwide overfishing has damaged oceanic ecosystems to such an extent that their ability to support increased fish numbers is significantly reduced. With better management of fishing programmes the fishing catch could in principle be increased; however, it is estimated that, annually, tens of millions of tonnes of fish are discarded from fishing vessels at sea, because they are not the species sought, a practice known as catch and discard and also used to avoid fines where fishing catches exceed local quotas.
The decisions governments have to make regarding the conservation of remaining fish stocks are not simply based on scientific recommendations but include economic and social factors too. The imposition of fishing bans can have an immediate and highly damaging impact on fishing communities and their support industries. In some cases, such as on the east coast of Canada and the USA and many ports along the North Sea coast, fishing quotas have permanently driven long-established fishing communities from their traditional livelihoods.
In 2013, reforms to the European Union's Common Fisheries Policy were agreed, banning catch and discard in open ocean fishing of certain species (such as mackerel and herring) from 2015, and extending this to other fisheries in 2016. The reforms also include a commitment (legally binding from 2014) to sustainable fishing, to be achieved by member countries working together in regions, with annual quotas based on scientific advice.