Aquaculture is the farming of aquatic organisms such as fish, shellfish and seaweed. Fish farming usually means rearing fish in tanks, ponds or net cages in lakes and the sea, for example salmon in Scottish sea lochs and carp or tilapia in ponds. About half of the fish eaten worldwide now comes from aquaculture.Advantages:
• it can reduce fishing pressure on wild stocks;
• production is reliable and controlled, with fish fed a high-protein diet and harvested at the best size;
• fish convert food into biomass efficiently, because as ectotherms they use little energy keeping warm and water supports their weight;
• it provides jobs in rural and coastal areas.Disadvantages:
• carnivorous fish such as salmon are fed on fishmeal and fish oil made from wild-caught fish, so wild stocks are still used;
• high stocking densities spread disease and parasites such as sea lice, which can pass to wild salmon swimming nearby;
• antibiotics and pesticides used to treat them enter the environment, and overuse of antibiotics can select for resistant bacteria;
• uneaten food and faeces add nutrients that cause eutrophication near the cages;
• escaped farmed fish may breed with wild fish, reducing the genetic diversity and fitness of wild populations;
• coastal habitats such as mangrove forests have been cleared for shrimp ponds.Aquaculture is more sustainable when herbivorous fish (such as carp) or filter-feeding shellfish (such as mussels) are farmed, stocking densities are lower, and feed is made from plant protein or waste products.
• it can reduce fishing pressure on wild stocks;
• production is reliable and controlled, with fish fed a high-protein diet and harvested at the best size;
• fish convert food into biomass efficiently, because as ectotherms they use little energy keeping warm and water supports their weight;
• it provides jobs in rural and coastal areas.Disadvantages:
• carnivorous fish such as salmon are fed on fishmeal and fish oil made from wild-caught fish, so wild stocks are still used;
• high stocking densities spread disease and parasites such as sea lice, which can pass to wild salmon swimming nearby;
• antibiotics and pesticides used to treat them enter the environment, and overuse of antibiotics can select for resistant bacteria;
• uneaten food and faeces add nutrients that cause eutrophication near the cages;
• escaped farmed fish may breed with wild fish, reducing the genetic diversity and fitness of wild populations;
• coastal habitats such as mangrove forests have been cleared for shrimp ponds.Aquaculture is more sustainable when herbivorous fish (such as carp) or filter-feeding shellfish (such as mussels) are farmed, stocking densities are lower, and feed is made from plant protein or waste products.