Fishing activities have various negative impacts on marine ecosystems. The greatest cause for concern is the rapid depletion of fi sh population due to extensive commercial fi shing. In 2002 72% of the world's marine fi sh stocks were being harvested faster than they can reproduce. Bycatch – the harvest of fi sh or shellfi sh other than the species for which the fi shing gear was set – accounts for a quarter of the total catch (27m tonnes in 2003) and much of it is lost.