Fish are a renewable resource, but overfishing (catching fish faster than the population can reproduce) has caused many fish stocks to collapse. A well-known example is the cod of the Grand Banks off Newfoundland, whose fishery collapsed in the early 1990s; North Sea cod stocks also fell sharply.Overfishing removes breeding adults and young fish before they can reproduce, disrupts food webs, and bycatch kills non-target species such as dolphins, turtles and seabirds.Methods used to make fishing sustainable include:• Fishing quotas: limits on the mass of each species that may be caught, based on scientific estimates of stock size
• Minimum mesh size for nets: young, small fish escape, survive and reach breeding age
• Minimum landing size: fish below a certain size must not be kept
• Closed seasons: no fishing during the breeding season
• Protected areas and no-take zones where fishing is banned, allowing stocks to recover and spread into surrounding waters
• limiting the number of fishing boats or the days they spend at sea
• banning damaging methods such as bottom trawling in some areas
• fish farming (aquaculture), which reduces pressure on wild stocks, although it can cause pollution, disease and parasite spread to wild fish.These measures only work if they are enforced and agreed between countries, because fish populations cross national boundaries. They can also cause economic hardship for fishing communities in the short term.
• Minimum mesh size for nets: young, small fish escape, survive and reach breeding age
• Minimum landing size: fish below a certain size must not be kept
• Closed seasons: no fishing during the breeding season
• Protected areas and no-take zones where fishing is banned, allowing stocks to recover and spread into surrounding waters
• limiting the number of fishing boats or the days they spend at sea
• banning damaging methods such as bottom trawling in some areas
• fish farming (aquaculture), which reduces pressure on wild stocks, although it can cause pollution, disease and parasite spread to wild fish.These measures only work if they are enforced and agreed between countries, because fish populations cross national boundaries. They can also cause economic hardship for fishing communities in the short term.