environmental and biological factors.

Discarding patterns are influenced by catch compositions, which in turn are determined by environmental factors, such as recruitment of small fish into the fishery, and social factors, such as quota regulation, choice of fishing gear and fishers' behaviour. There have been numerous studies on the scale of discarding. In the North Sea the total annual quantity of discards has been estimated at 800,000-950,000 tonnes, or the equivalent of one-third of the total weight