Bycatch: innocent victims.

More than 27 million tonnes of "untargeted" fish and other marine creatures are caught and thrown away each year by the world's fishing fleets. That's almost a third of the total world catch. The vast majority of this "bycatch" does not survive. Bycatch is usually the product of unselective gear and unselective fishing practices. Some fisheries involve much more of this waste than others, but nearly all fisheries involve some amount of bycatch.

Avoiding bycatch makes fishing more of a science than many fishers are accustomed to. Skippers need to be mindful of water temperatures, gear placement, bottom types, and the exact position of their boats in relation to areas that are closed. They need to avoid areas with mixed stocks as well as migratory, breeding, and nursery areas. They also need to use fishing gear in a way that excludes this untargeted catch.

Fisheries that use small-mesh fishing nets of the sort used for shrimp and small fish have the most bycatch, but even large mesh nets can do serious harm. Gillnets and driftnets, if placed improperly or left in the water for too long, can drown large numbers of marine mammals, birds, and sea turtles. Nets of all kinds that have been lost or discarded by fishers (so-called ghost-nets) can drift with ocean currents for years, continuously killing sea creatures of all kinds.

Nets are not the only problem. Long-lining is a common type of hook and line fishing that can involve excessive bycatch if used in the wrong areas, at the wrong depth, or if left in the water for too long a time.

The shrimp trawling industry has by far the worst bycatch of any fishery. For every kilo of shrimp landed, at least five kilos of small and juvenile fish are caught and pitched out. In some areas the ratio is said to be 10 kilos of bycatch per kilo of shrimp. Changes to the trawling gear, such as the sea turtle and fish excluders required on U.S. trawlers, can significantly cut down on this bycatch. Unfortunately, shrimp trawling fleets of many other nations often fish without such gear modifications. The World Trade Organization recently decreed a U.S. law as an unfair trade practice because it required shrimp fleets of other nations to use turtle-excluder devices if they want to import their product into the U.S.

CURTAINS OF DEATH

Drift nets hang like a curtain from floats on the water's surface. Some drift nets are up to 95 kilometres in length. Drift nets virtually strain huge swaths of the ocean catching everything in their path. Some species are commercially useful others are not, but they all die in the drift nets. An international campaign led to a United Nations voluntary ban in 1992, but Italy, France, Ireland, and other nations continue to allow their use, according to the World Wildlife Fund.