05 Oct Sustainable aquaculture – impacts on environment
Aquaculture and environmental impacts
Aquatic ecosystems, inland, coastal and marine, provide humans with resources for recreation, food and livelihood. They are used by both capture fisheries and aquaculture as well as other competing sectors. Achieving sustainable use of aquatic ecosystems has been the main objective of fisheries management for decades.
Ecosystems can be described at various sizes and with different degrees of resolution, from the Earth or a whole ocean with their large scale relations and processes, to a microscopic grain of sand and its immediate surroundings. The choice is based on pragmatic considerations.
The exploited ecosystem is unavoidably affected by fishery activities. Wild or ranched stocks and other organisms affect each other e.g. through predator-prey relationships or transfer of diseases. (Source: http://www.fao.org/fishery/ecosystems/en)
Aquaculture — the farming of fish, shellfish and aquatic plants — as a sector could boost economic growth across Europe and bring social benefits through new jobs.
Presently, a quarter of seafood products consumed in the EU (including imports) are produced on farms. There are over 14.000 aquaculture enterprises in the EU, directly employing 85.000 people in total. In contrast with other regions of the world, aquaculture production is stagnating in the EU, while imports are rising.
Aquaculture has an important role to play in food security as well as its economic growth but we, also, have to have in our mind the impacts on the environment.
POLLUTION AND AQUACULTURE
Organic waste and nutrient pollution
Organic waste and nutrients are released by fish farms, especially open farms, from which waste and water flows freely. Waste is released as solid particles (e.g. fish faeces and uneaten feed), while dissolved nutrients (nitrogen and phosphorus) are released by fish (through their gills and in their urine), as well as by the solid waste when it breaks down. These can negatively affect benthic (seafloor) ecosystems in the local vicinity of the farm, causing ecological impacts. Nutrients released from fish farms have the potential to cause eutrophication.
Pharmaceuticals and pesticides
Aquaculture farms often provide conditions which allow disease to flourish more easily; for example, animals are often stocked at a higher density than wild fish. Most veterinary products and disinfectants to manage animal disease have been judged to have minimal negative environmental impacts if used correctly (IUCN, 2007). Many sectors of aquaculture, such as shellfish farming or most extensive pond farming, use no medicines, and pharmaceutical use is closely regulated and inspected in all EU Member States. However, problems, such as risks to non-target species, may occur where pharmaceuticals or disinfectants are used above safe limits. It is also possible, in view of uncertainties regarding potential effects, that the use of some products even within those limits might create problems for nontarget species.
Antifoulants are chemicals applied to aquaculture equipment, such as cages and ropes, to reduce ‘biofouling’ — the unwanted growth of plants or creatures, such as barnacles, on their surface. Controlling biofouling is one of the most challenging — and expensive — production issues for the industry. Most antifoulants use copper as their active ingredient, which can leach into the environment. Its toxic effects on various non-target species have been documented. It can also contaminate seafloor sediment around farms.
Fish can escape from farms as a result of human error during handling, mechanical failure or damage to pens by weather or predators, such as seals and dolphins. Escapes are more likely to occur from open farms than closed farms. Some species of escaped fish may breed with wild fish. Farmed fish typically have different genetic characteristics to their wild counterparts. These traits reduce their ability to survive and breed in the wild, however, if they do manage to breed, may be passed on to wild hybrid offspring . Genetic mixing can also occur if fish release fertilised eggs from open farms into surrounding waters.
Diseases can pass between wild and farmed species. Most cases of new diseases in European native, wild species are introduced by no nnative, aquaculture species (Peeler et al., 2011). For example, the parasite Anguillicoloides crassus, which was introduced to Europe through imported Asian eels from Japan to Germany, now infects wild European eels across many countries. It spread even though farmed eels did not escape and is thought to have contributed to European eels’ dramatic decline over the last 20 years, together with other factors including habitat loss, pollution, fisheries, predators and obstacles to migration, such as hydropower. In aquaculture, a subject of much debate, is the question of as to what extent the spread of sea lice from sea cages. Intensive salmon farms provide good conditions for sea lice growth and transmission, compared with the wild environment, and outbreaks of this parasite are one of the biggest problems for operators.
Wild fish for feed
In recent years, wild fish have come to be used much more efficiently in feed.
Environmental impacts of harvesting fish for feed in European seas can include: seabed damage caused by trawling and disruption of ecosystems and food chains — reducing prey for other fish and seabirds.
Environmental concerns are already recognised by the aquaculture industry, which has made great progress in improving its environmental record in recent years. Research has shown that some environmental pressures can been mitigated in absolute terms, as seen with the dramatic reductions in escapes and antibiotics use in Norwegian salmon farms. Significant improvements in efficiency have also been noted, as with the reduction of wild fish used in feed. Technological and biological (through selective breeding) developments will enable further relative improvements, only if ecological interactions can be managed appropriately. As the sector expands further, it must consider how to continually improve its environmental sustainability: this is essential to the long-term economic sustainability of aquaculture as well as to our food security.
Scientific evidence must continue to play a central role in this industry, informing best practice. Ongoing applied scientific research is needed to develop practical solutions to environmental problems. It is also clear that research into the very ‘basics’ of marine/aquatic ecology and processes is needed, from which better practical solutions can be developed. Consumer demand and policy developments are also central in shaping the future of aquaculture. In the future will be required to carefully plan the co-location of marine activities, such as aquaculture, shipping and offshore energy. This should ensure that all activities can benefit from synergies and that any negative environmental impacts can be minimised through their early identification.
Source: Science for Environment Policy, European Commission, (http://www.feap.info)
You can read the complete briefing here