| Policies for Aquaculture Development |
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Does Aquaculture Give Healthy Food
Fish and shellfish benefit from a deserved reputation of comprising food that is nutritious and give a range of recognised health benefits.
There would not be much point in practising and developing aquaculture if the products were not good or satisfying for the consumer, from a visual, taste or health point of view. While shellfish production is directly influenced by its surrounding environment (for most species, there are virtually no external nutrient inputs), most of European fish farming uses manufactured compound feeds for the growth of the fish. The herbivorous carps, which have a lower value than most other species reared in Europe, are virtually the only species reared in Europe where compound feeds are rarely used. While the term 'artificial' feed is often used, compound feeds are made with naturally-occurring ingredients.
Since 'you are what you eat', a great deal of research has been done on the nutritional requirements of fish that are or could be farmed. Not surprisingly, there are many differences in requirements between species; a cold water salmon does not have the same diet as warm water bream, a freshwater trout does not eat the same food as an eel. It is not that long ago (about 30 years ago) that fish farmers would use minced 'trash' fish as a diet and the development of compound feeds, tailored to the nutritional needs of the species, provided huge technical advances for the profession.
If the most notable development was the reduction in the amount of feed (in weight) required to produce, say one kilogramme of fish, the immediate side-effects include:
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Evidently, the manufacture of a compound feed has to include the appropriate ingredients, as well as the best manufacturing procedures, to give the required results. In Europe, there are several companies and research institutes that have been to the fore, on a global scale, in the successful development of the best available feeds.
Evidently, the ingredients of the feed provide the key to whether the final product is a healthy one to eat.
Aquaculture provides excellent healthy food but can be subject to criticism at times. Shellfish culture can be affected negatively by the environment in which it is practised (e.g. marine pollution), usually by elements which are largely outside of the control of the farmer, whose prime goal is to provide the best product, in a competitive market, for the consumer. Fish farming can also be affected by pollution of the water in which the fish are reared, both marine and freshwater, which is one of the reasons why so much care and attention is paid to site selection (in areas where pollution is likely to be minimised). Fish require food in order to grow and most fish farms in Europe are classified as being 'intensive', which means that 'artificial' feeds are used. 'Artificial' does not mean that the feed ingredients are manufactured but that the feed is a compounded mixture of the nutrients that the fish require for a complete diet. A substantial document on this topic can be found within Aquamedia that explains the issues and circumstances concerning fish feeds and their ingredients.
Heart disease and strokes are primary causes of death and serious illness among European men and women and a 'healthy' diet is recognised as being one of the key contributors to good health. Obesity ranks as one of the most rapidly expanding clinical conditions affecting health in the European Union and which is, in most cases, strongly influenced by diet. A high consumption of 'Junk' food and imbalanced diets are known to be important contributing factors to this condition.
The main claim to fame put forward for eating fish has been its importance as a source of the long chain n-3 polyunsaturated fatty acids (known as PUFAs), eicosapentaenoic acid (EPA) and docasaheaxaenoic acid (DHA).
There is only one form of living organism that can readily make long chain n-3 PUFAs - marine algae. As fish feed on algae, they become rich sources of such fatty acids. This is particularly true of the flesh of oil-rich fish such as mackerel, salmon and herring, as well as the livers of any 'white' fish (e.g. cod).
Fish is also a reliable source of protein, iron, selenium and iodine. The flesh of oil-rich fish and particularly the livers of lean white fish are good sources of vitamins A and D. When the bones are small and soft and can be eaten (e.g. in sardines, pilchards, tinned salmon) fish is also a useful dietary source of calcium. Fish is a rich source of a large number of minerals. Shellfish particularly tend to accumulate and store trace elements from their surroundings and are one of the richest sources of zinc available with recorded levels of up to 100 mg/100g and also provide a valuable vitamin resource (riboflavin, niacin…). More recently, attention has been drawn to the benefits of taurine - an amino acid that is found in fish and animal proteins - which appears to have several beneficial effects, notably on the liver and the dilation of arteries.
Concern was raised in respect of the aquaculture sector with the outbreak of 'Mad Cow Disease' and when awareness of the potential for dioxin and PCB contamination was raised.
'Mad Cow Disease' is incurred by infectious agents known as 'prions'. A prion has been defined as "small proteinaceous infectious particles which resist inactivation by procedures that modify nucleic acids". The discovery that proteins alone can transmit an infectious disease has come as a considerable surprise to the scientific community.
Prion diseases are often called spongiform encephalopathies because of the post mortem appearance of the brain with large vacuoles in the cortex and cerebellum. Most mammalian species appear capable of developing prion diseases (sheep, cows) and it is believed that humans can also contract such diseases (e.g. Creutzfeld-Jacob Disease, Kuru…) through the consumption of contaminated material (see http://www-micro.msb.le.ac.uk/335/Prions.html) .
Until now, from data available from current research, there is no evidence that edible fish or shellfish have any link to the causal mechanism of prion diseases and concern was raised as to the incorporation of animal by-products in compound feeds for aquaculture.
Animal meat or bone meal is not used in fish feed manufacture and the post-BSE legislation imposes that the use of animal products for incorporation in feeds must be proven to be free of risk to human health.
The European Commission's White Paper on Food Safety identified the need to define standards for contaminants in the chain 'feed to food' and the Scientific Committees for Food and Animal Nutrition published reports on the matter in 2001.
The contamination of animal feeds with dioxin and dioxin-like compounds raised general awareness of the need for improved control measures throughout the entirety of the food chain. The main source of dioxin contamination is from industrial activities (e.g. paper manufacture) that release air-borne or water-borne compounds that contaminate the environment. The dioxins and similar compounds are highly fat-soluble (lipophilic) and are taken up, for example, in the seas and oceans by micro-algae. As the micro-algae enter the food chain of fish and shellfish, this is how fish and shellfish can be contaminated. On land, it is rainfall and the uptake of dioxins in cereals and fodder that leads to the contamination of dairy products and meats.
All food materials, including fish and shellfish, contain levels of dioxins and PCBs but data is not yet clear enough to be able to provide clear 'health' decisions on all food products. A great deal of research is being done at the present in order to clarify this position. Nonetheless, tests that have been made on fish produced by aquaculture indicate clearly that it is the content of these compounds in the food given that most strongly influence any measurable contamination of the fish. European legislation on this matter has set strict maximum limits for the presence of such contaminants in aquaculture feeds.
While this seems pretty scary, one must remember that dioxin levels are much lower now than 30 years ago - the 'background' contamination is estimated as dropping at a rate of 6-10% per year and by 2002 the dietary intake of dioxins had fallen by some 75% over a twenty year period. Life expectancy has never been higher and the 'pros' and 'cons' have to be evaluated in a pragmatic manner.
As an example, mother's milk is the earliest and most concentrated exposure to dioxins faced by a newborn baby - due to long term accumulation by the mother. However, the additional benefits gained from mother's milk (immunity to disease, nutrition…) are seen to largely outweigh the risk posed by dioxins.
Research is still required for the absolute scientific analysis of the risks posed by the consumption of different food products, including aquaculture products, and the EU generally follows the position of the WHO (World Health Organisation) on these matters. Important risk (reduction) factors are built in to all recommendations (Recommended Daily Intake) in order to provide the safest consumption levels for human diets.
Not surprisingly, one of the principle fears of mothers for serving fish is the presence of bones but most aquaculture fish are available as fillets where the bones have been meticulously removed.
In this era of improved public awareness of food quality, a more pragmatic approach to diet is developing but this remains strongly influenced by purchasing power. Expensive food that is good for you may be replaced by convenience food that is not so good - but personal choice combined with the availability of an affordable product and, in this day and age, the information required for an informed purchase are determinant factors for consumption.
As in any activity, some farmers are better than others and may produce better products - however, this is a reflection of quality rather than the safety of the products. The legislator, the feed manufacturers and the farmers are all acting to provide the safest and most nutritious products of the highest quality possible for the consumer.
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