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written by Professor Hans Ackefors and Mr. Patrick White (Part 3)
This paper was published earlier in World Aquaculture - June 2002, Volume 33, No2 and has been provided with permission from the authors
Regulation
All industries are dependent on a legal framework for their growth and development, including environmental regulation, and both central and regional support are necessary for any modification. Many authorities propose environmental quality standards (EQS) for every industry which, in the case of aquaculture, will select the water bodies available for production sites.
Environmental quality criteria are typically the composition of benthic fauna and various standard quality values for the bottom sediment and the water column. It is also important to know the capacity of the receiving waters to absorb any organic and inorganic wastes from future aquaculture sites. Such calculations are made in countries which permit intensive fish farming in floating complexes.
Setting EQS is a regulatory function which benefits both the environment and the producer. Good water quality around the site is also a prerequisite for good product quality. Poor site conditions, such as contamination with bacterial, chemical, or natural toxins, must be avoided, and therefore it is necessary to monitor key parameters for signs of trouble. Maintaining high EQS is also a prerequisite of good husbandry practices, such as prevent disease outbreaks directly or pre-empt outbreaks through vaccination or other preventative measures.
Member states of the European Union now require new aquaculture ventures to make an environmental impact assessment, or EIA, before a license is granted. This is a difficult demand, as the impact depends on the scope of activity at the site, and in particular the quality of the receiving waters. Predicting nutrient loading relative to the capacity of the receiving waters requires considerable technical competence.
Monitoring coastal aquaculture operations has been proposed by FAO's Group of Experts on the Science Aspects of Marine Environmental Pollution (GESAMP). Its 1996 recommendations embrace:
• Regulation, which includes (i) compliance with terms of license (ii) protection of the natural environment, and (iii) safeguarding water quality
• Farm management, which includes (i) optimizing husbandry practices (ii) control of water quality, and (iii) limiting interference from other aquaculture operations
• Public health, which includes protection of product quality
Monitoring, and monitoring technology, depend on a specific farming system and practice. Therefore, to evaluate the discharged water, it is necessary to consider the level of production, the feeding technology, the quality of feed, and the capacity of the receiving waters.
Feed and Feeding Practices
The content of phosphorous and nitrogen in the feed, and the feed conversion rate, are important factors to consider when assessing the possible impact of waste products at an aquaculture site. Mass-balance calculations are used to calculate the actual level of pollutants, specifically nitrogen and phosphorus. In the last ten years, with increasing scientific information, the feed coefficient for the advanced marine aquaculture practices has decreased from 2.3 to less than 1.3. At the same time the nitrogen content in the feed has decreased from 7.8 to 6.8%, and the phosphorous content from 1.7 to <1%. This means that, for every ton of fish produced, the discharge of phosphorus is now <10 kg and nitrogen <53 kg. Current research indicates that it is possible to reduce these discharges even more.
Feed Quality
The way an artificial feed is fabricated is of utmost importance in the reduction of waste from aquaculture units. Extruded pellets, for example, have a slow sinking speed and remain intact for a long time. Therefore they are more available to the fish than compressed pellets, which not only sink faster but disintegrate earlier.
The composition of the feed is equally import, and the basic formulation contributes to the output of wastes. For example, a typical composition of a salmonid feed is now fat (30%), protein (40%), carbohydrate (13%), with an energy content of 19.2 MJ /kg. Thus the nitrogen content is now about 7%, and as the fish utilizes fat instead of protein for energy, lower volumes of nitrogenous compounds, such as ammonia, are excreted.
Similarly there is less excretion of phosphorus since it has been reduced to about 1% in the diet. The bio-availability of dietary phosphorus is influenced by several factors, including its chemical form, digestibility of the diet, particle size, interaction with other nutrients, feed processing, and water chemistry.
Feed Management
Feed is the costliest item in the operational budget of most fish farms, and the optimum use of feed depends on several factors. These include not only the size and quality of the feed, but the size and age of the fish, environmental conditions, such as light and water temperature, and even fish behavior.
Several computer programs have been designed to optimize feeding within seasonal and daily variations in all these parameters, but the fundamental requirement is to avoid waste. Therefore, as teleostean fish express feeding periodicity, less costly solutions include automated feeders and demand feeders, both of which use behavioral responses. Some incorporate an echo-sounder which observes behavioral responses and then regulates the feeder as the fish become satiated and move away. Where practical, any uneaten feed can be collected at the bottom of the unit.
Feed management has been further improved since the margins of profit for most fish farms have become very fine, and time-restricted demand feeders have become more common. These restrict feed delivery to a number of predetermined periods each day, but it is necessary to disperse the feed over the whole area so that all the fish, not only the largest and most aggressive, can obtain their ration. These feeders can possibly reduce feed wastage by a further 40%.
Reduction in Bio-wastes
Various technical devices have been designed to collect feed wastes, nutrients, organic material, and dead fish from production units. The possibility for collecting and treating wastes from on-shore systems is much better than for offshore systems. Onshore, it is relatively simple to treat wastewaters from ponds, tanks, and other units with traditional wastewater techniques, such as screening and filtration followed by treatment ponds and settling ponds.
Recirculation is another shore-based technology which is suitable for complete control over the collection and treatment of wastes. Because of its high cost, it is currently being used only in hatcheries, where volumes are small, and farms raising high-value crops outside their natural range; for example, in temperate climates for warm-water species, such as eel and African catfish, and for sturgeon which requires >20°C temperatures for optimal growth.
Recirculation again integrates many traditional waste-treatment technologies, such as screens, gravel and trickling filters, and biofilters. More comprehensive systems may have denitrification units, ultra-violet disinfection, and possibly ozonation. The cost benefits are in the saving of water and energy, and total control of waste. There are also benefits in disease control.
Pathogens are easily spread in a water medium. Therefore confined fish are more likely to have a disease epidemic than free-ranging wild fish, as it may be exacerbated by conditions of stress and possibly nutrition.
However, pathogen organisms occur naturally in both captive and wild fish, and there can be epidemics in even the most well-managed farm operations. Consequently preventative measures, including approved veterinary medicines, drugs, and chemicals, have always been taken to combat diseases in farm animals, including fish. But the traditional antibiotics have now been largely replaced by vaccines, and even these in turn will probably be superceded by probiotic feeds. As micro-flora in the gut play an important role in the well-being and health of fish, they are now being added experimentally to the feed, or even to the water, with good results.
Pathogens and the resultant diseases that infect both aquatic animals and plants, together with preventative measures and treatments, have been widely reviewed. Considerable importance has also been attached to the issue of residual drugs and veterinary medicines in natural populations, in the sediments and substrates near farms, and in the farm products. Currently, monitoring is one effective control which, in the case of the products, is invariably handled by government authority. Others are preventative medicine and effective treatment. There is still a wide range of chemical treatments used in aquaculture and there is good reason for their safe use.
Product Quality and Consumer Safety
Aquaculture products compete in an open market, and must therefore be of the highest possible quality. Until a product commands its own niche, this means a fresh and nutritious product with protein, lipid, and carbohydrate composition comparable to wild fish. It must have a taste appealing to consumers, and be free of any health hazards.
Therefore regulations and protocols for the use of chemicals and antibiotics in the production of farm animals must be strictly followed. It is necessary to observe the required withdrawal time before harvest, according to the directives from the food and hygiene authorities. Similarly, post-harvest treatment must comply with the regulations for proper and humane treatment of animals, and processing must comply with accepted hygienic and safe practices for the handling of food for human consumption.
Trends in Consumer Preferences
In many countries the consumers have created their own organizations and proposed rules or requirements for the food they wish to buy. Some of them now consider organic farming or ecological farming important. Although their market may still be small, their principles send a message to all food producers about, for example, concern for animal welfare, the type of technology adopted, the source of feed components, use of veterinary medicines, etc. Seafood is not exempt, and in some countries aquaculture producers are responding by growing and labeling organically-raised products which, they claim, are superior to traditionally farmed fish which justifies a higher price.
With regard to aquaculture, the concerns of these new consumer organizations mostly relate to the welfare of the fish and the feed. For example, the intensive environment in which the fish are raised, and the fact that other fish are the major source of protein in their feed, are primary issues. Another is the broad issue of a negative impact on the environment, which consumers may interpret as a water quality problem, genetic manipulation, or competition with wild stocks.
These increasing social trends mean that producers must adapt to the preferences of the consumers if they wish to obtain that part of the seafood market, and adapt their own Codes of Best Practice (CBPs) to produce products with the required quality. In some cases the requirements may seem a little unrealistic and add unnecessarily to production costs, but it is important for continuing dialogue between producers and consumer organizations, as exemplified by other segments of the food industry.
Conclusion
In conclusion, a Code of Best Practice (CBP) must be designed around the interests of the farm animals themselves as well as the interests of (local) people and consumers. The interests of the farm animals must take into account their life-histories, physiology, and behavior, together with the proposed culture technology, and pre- and post-harvest handing. The interests of the people must include all the positive and negative impacts on their social and economic environment, and on the ecological environment of the farm site. Although a CBP will have some general principles which will apply throughout the breadth of the industry, the diversity of aquaculture, with its many species and production systems, necessitates almost an individual CBP for each sub-industry.
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