Cage culture: seabass, seabream and red drum,mainly in
Méditerranean waters including Provence Côte d'Azur, Corsica
and in tropical areas around Mayotte and La Réunion.
Fish are raised in large mesh cages, floating at the surface of an open body of water and anchored onto the ocean floor. The cages are set in semi-sheltered zones off the coast, where the site has currents strong enough to keep the site well oxygenated and reduce environmental impact (since an aquaculture site with poor mixing conditions is likely to cause local excess of nutrients which can be fatal to marine organism); but is sheltered enough that cages will not run the risk of getting carried away during storm events.
Due to the increasing competition that exists on the coastal front (between tourism industry, residences, etc.) the aquacultural industry is gradually being forced to move their sites inland or offshore, with new systems able withstand harsher conditions out at sea.
Freshwater systems: trout, carp, tench, roach, pike and sturgeon
Fish are raised in ponds or cages, fixed to the bottom of rivers or lakes. Fish farming can be either extensive (ponds), intensive (basins), or semi extensive (basin).
Extensive – low level of intervention in the rearing process, low fish densities; natural food sources and low stocking density (so to eliminate the need for artificial water aeration and exchange systems).
Intensive – high level of intervention in the rearing process, high stocking density; supplemental feeding, use of organic and inorganic fertilizers, water aeration and exchange systems and, at times, environmental manipulation.
Semi-extensive – intermediate level intervention in the rearing process, medium stocking density; supplemental feeding complementary to natural feed.
Cons
• Nutrient pollution: accumulation of excess nutrients below cages (from feed, fertilizers and excretion).
• High risk of parasite and disease spread among individuals (especially in overpopulated sites), and into the surrounding environment.
• Antibiotics used to fight parasites and disease seep into the surrounding environment, polluting wild ecosystems.
• Invasive species: if non-native species are being raised in an open water system, the escape of individuals may upset the natural balance of the environment.
• The mesh that makes up the cages is often source of bycatch of birds and marine organisms.
The quality of fish rearing and level of sustainability of the aquaculture industry varies from one site to another even if the same general rearing technique is used.
Ponds on land – fish are reared in large basins equipped with water flow-through systems or re-circulation systems.
Freshwater ponds: eel, trout, carp, sturgeon, tilapia, pangasius
marine water ponds: sea bass, salmon, turbot,...
Flow-through system – open circuit: water is taken from a river upstream, circulated once through the basin and then released back into the river downstream.
Flow-through systems: seabass and trout
Pro
• Low energy demand.
Cons
• Excess organic matter is released into the surrounding freshwater system ad may cause eutrophication.
• High freshwater consumption.
Highly re-circulated systems – closed circuit: water exiting the basin is filtrated, oxygenated and re-circulated back into the basin.
Highly re-circulated systems: seabass and trout
Pros
• Better control over environmental conditions (temperature, pH, salinity,....)
• No or little release of organic waste into the environment; water can be treated before being returned to nature.
Cons
• High energy costs.
• High capital costs.
New systems are being developed using phytoplankton and filter feeders (eg mollusks, oysters, mussels,..) to recycle nutrients and eliminate waste from ponds and basins.
The dietary requirement of aquatic organisms (i.e. carnivorous vs. herbivorous) is an important factor that must be taken into account when assessing the level of sustainability of an aquaculture business.
Most fish raised in France are carnivorous (i.e. salmon, sea bass, . Their feed consists of fishmeal and fish oil produced from wild small pelagique fishes (i.e. sprat, mackerel, sand-eel,...) harvested from wild stocks. On average, 2-5 pounds of bait are required for every pound of fish produced.
Since each fish requires huge quantities of wild fish to feed them, those systems heavily impact wild stocks. 5 pounds of fish must be harvested to produce 1 pound of fishmeal and 20 pounds of fish must be harvested 1 pound of fish oil. Moreover, fishmeal and fish oil fleets are, for the most part, located in South America (primarily Chile and Peru) where the product is processed and shipped to Europe, which significantly increases the industry’s carbon footprint.
Herbivorous fish like tilapia are therefore a better choice in seafood consumption. Nonetheless, certain farms have been known to use fish protein as food additives in order to accelerate fish growth. It is therefore better to know the
Food additives are often added to enhance fish coloration and fertility rates. These chemicals may seep through the surrounding environment and affect wild fauna and flora. It is therefore important to stay informed on the origin of the fish and avoid those fed food additives
Studies are being carried out to try and reduce the negative impacts that the agriculture industry is currently exerting on wild stocks. Industries are seeking to create vegetarian fish feed that would contain as great a quantity of essential amino acids and fatty acids than products of fish origin contain. Still, feeding carnivorous species to high of a vegetarian to carnivorous feed ratio deteriorates the quality of the fish itself, altering the taste and texture of the product. It is therefore a necessity for the industries to provide carnivorous fish with a minimum amount of fishmeal and fish oil (25% and 30% respectively).
Fish farming performed within the European Union (EU) is regulated by a set of national and communal law. Those outside the EU borders must follow EU regulation if they are to export their products into the EU. French aquaculture industries are under strict monitoring the European environmental practices.
For more information about new regulations and guidelines to sustainable aquaculture, click on the following link:
http://www.feap.info/FileLibrary%5C10%5CIUCN_book_web.pdf
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A number of different methods are used to culture clams, oysters and other shellfish.
Pros
• Shellfish farming is often the most sustainable type of aquaculture present.
• Shellfish feed off naturally occur plankton.
• The success of shellfish farming is highly dependent on the quality of the site of production, thus it is a priority for shellfish farmers to keep waters clean.
Cons
• Sediment accumulation beneath the farming system.
• Introduction of invasive species into the environment.
• Introduction of parasites and diseases into the environment when farmed mussels are used to repopulate depleated wild stocks.
• Dredging wild seed beds to obtain seeds and dredging to harvest full grown shellfish in bottom cultures has a negative impact on the seafloor.
Bottom bags and posts – mussels are transplanted onto wooden poles or mesh bags on which they grow.
Suspended rope culture – mussel seedlings are set to grow on ropes suspended in the water thanks to a wood or plastic support system and kept in place by nylon nets.
Bottom culture – young mussels are harvested from the wild and set to grow on protected growing plots on the ocean floor and then harvested with dredges.
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Crustaceans are raised in ponds or brackish/marine water basins both inland and in coastal waters.
Shrimp are raised in open water basins in tropical and subtropical zones. Some attempts to raise them in ponds on land in temperate zones are currently being carried out.
Cons
• The building of shrimp farms in tropical and subtropical regions destroys mangroves forest, who play a crucial role in protecting shorelines and serve as nursery grounds for a wide variety of fish and invertebrates.
• Inland ponds leak through to the surrounding environment creating saline conditions in ground water and agricultural crops.
• Shrimp are fed large amounts of fish-derived food.
• The metabolic wastes, feed wastes and antibiotics (when used) pollute the environment adjacent to the farm.
• Harvesting larvae from wild populations may negatively impact on wild populations.
• Shrimp farming is often a source of social conflict over who gets to obtain ownership of the shoreline (especially in developing countries).
• Spread of diseases and parasites into the surrounding environment.
In the past decade, a number of shrimp farming industries have made significant efforts to reduce the environmental impacts of this industry (reduction in chemical product use, protection and rehabilitation of mangrove forests,...).
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Sources:
Seafood Choices Alliance Produits de la Mer. Guide des espèces à l’usage des professionnels. (2008)
http://www.seafoodchoices.org/resources/documents/FrenchSpeciesGuide_RevisedFinal.pdf
Food and Agricultural Organisation. Profils des peches et de l’aquaculture par pays : France. (2005) http://74.125.113.132/search?q=cache:XdMinVgsHioJ:www.fao.org/fi/website/FIRetrieveAction.do%3Fdom%3Dcountrysector%26xml%3DFI-CP_FR.xml%26lang%3Dfr+coquille+saint+jacques+peche+francaise&cd=10&hl=en&ct=clnk&gl=us&client=safari
Ifremer.
http://www.ifremer.fr/francais/index.php
Images:
http://www.emperoraquatics.com/aquaculture-recirculation-systems.php
http://pagesperso-orange.fr/turbert-granvillaise/chausey/chy-maree/chy-aquaculture.html
http://www.emperoraquatics.com/aquaculture-recirculation-systems.php
http://www.ifremer.fr/francais/index.php