Aquaculture
Aquaculture Facts
aquaculture supplies ¼ of all the fish that humans eat ¾ of this is finfish and shellfish – the rest is seaweed Currently 220 species of fish are farmed Asia accounts for 90% of this Aquaculture may well contribute to fisheries collapse Mollusc cultures rely on ambient plankton levels Finfish require formulated feed, where carnivorous species require vast quantities of wild caught fish Pens provide shelter from predators Fish are fed and medicated with antibiotics
High stocking densities:
Greater volumes of waste produced Greater chance of spread of disease
Fish meal/oil
Extensive or traditional aquaculture use little or no fish oil or fish meal; 80% of carp and 65% of tilapia Reliance on fish meal has rapidly increases over the past 3 decades, where aquaculture has the fastest growing demand for fish meal. Compared to poultry or livestock feeds which are only 2-3% fishmeal 8 of the 20 most captured wild species are used as fish meal: Anchoveta, Chilean Jack Mackerel, Atlantic Herring, Chub Mackerel, Japanese Anchovy, Round Sardinella, Atlantic Mackerel, European Anchovy Herbivores can use plant based proteins and oils but carnivores need fish meal/oil as it contains essential lysine and methionine amino acids not found in plants Many feeds contain excess ingredients as the dietary requirements of the fish are unknown, there are resources therefore being wasted. Marine finfish require >5kg of fish meal to produce only 1kg of farmed meat e.g. tuna, halibut, hake, seabass, flounder. Salmon and shrimp require approx. 3kg fish meal to produce 1kg meat Only 3 species of farmed fish (milkfish, catfish, carp) use less fish as inputs than is ultimately harvested, where the average required is 1.9kg of wild fish to produce 1 kg! The net gain from aquaculture is largely due to carp and molluscs
Ecological impacts of aquaculture
Habitat modification: o Many 100,000 ha’s of mangroves & coastal wetlands have been transformed into milkfish and prawn (shrimp) ponds. This has destroyed a nursery habitat and there is no longer protection from storms, there is reduced flood control and trapping of sediments. loss of mangroves also means less water filtration and less nutrient being omitted o Net gains are low considering losses of seagrass and coral reef habitat o 400g (est.) of wild fish lost from near-shore catches for every kg of farmed prawns Use of wild caught seedstock: o E.g. Bluefin tuna in south Australia o Raising wild fish to market size by reducing mortality rate o Bycatch can be massive; milkfish 85% bycatch o Destruction of 10 billion fry for 1.7 million milkfish fry Changes in food webs: o Small ocean fish already overexploited o Climatic shifts (El Nino) produce sharp population fluctuations o Negative impacts on seabirds, marine mammals, wild fish predators Introduction of non-native fish and pathogens o Escapees hybridise with wild fish stocks o Risk of spreading disease o Salmon species frequently escape; in NE Atlantic 40% of caught are of farmed origin, leads to increased decline of local populations Nutrient pollution o untreated waste water laden with uneaten food and fish faeces contributes to nutrient pollution, particularly near confined water bodies o management directed at reduced stocking and reduced feeding – rather than treating wastes
4 strategies to make aquaculture more sustainable: 1. Farm lower on the food web: Encouraging farming of omnivorous and herbivorous species Reduce fish meal and oil supplements in feeds; in tilapia and carp fish meal and oil is added to boost weight gain, however this is having a large effect on wild stocks. 2. Reduce fish products in feed: Cost of feed is the largest production expense Better to determine dietary requirements of farmed species Substitute plant and terrestrial animal proteins for fish meal
3. Integrated production systems Move to polyculture – several species in a pond Seaweed and mussels grow well in wastewater Human health issues need to be addressed also 4. Promoting sustainable aquaculture Need regulation of new farming facilities in sensitive environments Minimise escapes of fish (with fines?) Enforce strict disease control measures Govt.s subsidise ocean fisheries by 20-25%, thereby slowing the expansion of aquaculture
aquaculture supplies ¼ of all the fish that humans eat ¾ of this is finfish and shellfish – the rest is seaweed Currently 220 species of fish are farmed Asia accounts for 90% of this Aquaculture may well contribute to fisheries collapse Mollusc cultures rely on ambient plankton levels Finfish require formulated feed, where carnivorous species require vast quantities of wild caught fish Pens provide shelter from predators Fish are fed and medicated with antibiotics
High stocking densities:
Greater volumes of waste produced Greater chance of spread of disease
Fish meal/oil
Extensive or traditional aquaculture use little or no fish oil or fish meal; 80% of carp and 65% of tilapia Reliance on fish meal has rapidly increases over the past 3 decades, where aquaculture has the fastest growing demand for fish meal. Compared to poultry or livestock feeds which are only 2-3% fishmeal 8 of the 20 most captured wild species are used as fish meal: Anchoveta, Chilean Jack Mackerel, Atlantic Herring, Chub Mackerel, Japanese Anchovy, Round Sardinella, Atlantic Mackerel, European Anchovy Herbivores can use plant based proteins and oils but carnivores need fish meal/oil as it contains essential lysine and methionine amino acids not found in plants Many feeds contain excess ingredients as the dietary requirements of the fish are unknown, there are resources therefore being wasted. Marine finfish require >5kg of fish meal to produce only 1kg of farmed meat e.g. tuna, halibut, hake, seabass, flounder. Salmon and shrimp require approx. 3kg fish meal to produce 1kg meat Only 3 species of farmed fish (milkfish, catfish, carp) use less fish as inputs than is ultimately harvested, where the average required is 1.9kg of wild fish to produce 1 kg! The net gain from aquaculture is largely due to carp and molluscs
Ecological impacts of aquaculture
Habitat modification: o Many 100,000 ha’s of mangroves & coastal wetlands have been transformed into milkfish and prawn (shrimp) ponds. This has destroyed a nursery habitat and there is no longer protection from storms, there is reduced flood control and trapping of sediments. loss of mangroves also means less water filtration and less nutrient being omitted o Net gains are low considering losses of seagrass and coral reef habitat o 400g (est.) of wild fish lost from near-shore catches for every kg of farmed prawns Use of wild caught seedstock: o E.g. Bluefin tuna in south Australia o Raising wild fish to market size by reducing mortality rate o Bycatch can be massive; milkfish 85% bycatch o Destruction of 10 billion fry for 1.7 million milkfish fry Changes in food webs: o Small ocean fish already overexploited o Climatic shifts (El Nino) produce sharp population fluctuations o Negative impacts on seabirds, marine mammals, wild fish predators Introduction of non-native fish and pathogens o Escapees hybridise with wild fish stocks o Risk of spreading disease o Salmon species frequently escape; in NE Atlantic 40% of caught are of farmed origin, leads to increased decline of local populations Nutrient pollution o untreated waste water laden with uneaten food and fish faeces contributes to nutrient pollution, particularly near confined water bodies o management directed at reduced stocking and reduced feeding – rather than treating wastes
4 strategies to make aquaculture more sustainable: 1. Farm lower on the food web: Encouraging farming of omnivorous and herbivorous species Reduce fish meal and oil supplements in feeds; in tilapia and carp fish meal and oil is added to boost weight gain, however this is having a large effect on wild stocks. 2. Reduce fish products in feed: Cost of feed is the largest production expense Better to determine dietary requirements of farmed species Substitute plant and terrestrial animal proteins for fish meal
3. Integrated production systems Move to polyculture – several species in a pond Seaweed and mussels grow well in wastewater Human health issues need to be addressed also 4. Promoting sustainable aquaculture Need regulation of new farming facilities in sensitive environments Minimise escapes of fish (with fines?) Enforce strict disease control measures Govt.s subsidise ocean fisheries by 20-25%, thereby slowing the expansion of aquaculture
