Impact of aquaculture on environment
Young boy seeks shrimp fry in the Sundarabans mangrove forest (Bangladesh)
Aquaculture in common with many other sectors uses natural resources and interacts with the environment. However, aquaculture is increasingly confronted with issues of environmental protection. It is now generally accepted that increasing efficiency in resource use and minimizing adverse environmental interactions will be major goals for the next decades, which will require commitment and willingness to collaborate by all those involved, either directly or indirectly, in aquaculture development. Much of the current controversy is centered around environmental degradation resulting in some cases from inadequate coordination and management of development, as well as from irresponsible practices by some entrepreneurs risking to bring the whole aquaculture sector into disrepute.
Major environmental impacts of aquaculture have been associated mainly with high-input high-output intensive systems (e.g. culture of salmonids in raceways and cages) the effects of which included discharge of suspended solids, and nutrient and organic enrichment of recipient waters resulting in build-up of anoxic sediments, changes in benthic communities (alteration of seabed fauna and flora communities) and the eutrophication of lakes. Large-scale shrimp culture has resulted in physical degradation of coastal habitats, for example, through conversion of mangrove forests and destruction of wetlands, salinization of agricultural and drinking water supplies, and land subsidence due to groundwater abstraction. However, misapplication of husbandry and disease management chemicals, collection of seed from the wild (bycatch of non-target species occurring in the collection of wild seed) and use of fishery resources as feed inputs, are also causing concern. Mollusc culture has been held responsible for local anoxia of bottom sediments and increased siltation.
Aquaculture is the principle reason for the introduction of freshwater fishes and experience has shown that the introduced species will eventually enter the natural ecosystem (either through purposeful release or accidental escape). Thus, non-native species in culture can adversely impact local resources through hybridization and loss of native stocks, predation and competition, transmission of disease, and changes in habitat, e.g. burrowing, plant removal, sediment mobilization and turbidity.
Environmental interactions between aquaculture farms, can include self-pollution and transmission of diseases and occur in areas where the high density of farms forces use of water contaminated by neighbouring installations, with significant losses of farmed stocks and financial returns. Effects can also occur at a distance with interchange of living material between farms and a consequent spread of disease.
The pressure to use resources more efficiently, to increase competitiveness and to respond to market forces is resulting in some areas in trends toward intensification of aquaculture production. These are associated with more sophisticated farm management, shift to monoculture of high-value species, and the targeting of more affluent consumers. There is an increased risk that such trends to intensification will increase environmental impacts if inappropriate planning and management of such farming systems and, in particular, the inefficient use of resources and inputs such as equipment and chemicals, are not avoided.
Overall, stronger commitment to responsible aquaculture is needed. Not only producers, but also government authorities and general public, including consumers, are currently enhancing their awareness and knowledge of potential ecological impacts as well as of negative social and economic side-effects of a given aquaculture development. Experience has shown that Iimproved coordination and management of development initiatives at sectoral, eco-regional and local levels can contribute to more environmentally sustainable development of aquaculture.
Precautionary approaches are advocated for many aquaculture practices, particularly as regards the introduction and use of alien species. Special consideration must be given to better management of aquaculture developments affecting sensitive habitats, such as, for example, estuaries, mangroves, wetlands, riparian fauna and vegetation, or specific breeding and nursery grounds.
The benefits of applying and promoting precautionary approaches become more evident where environmental data and related information on farming performance and environmental effects have been generated. Development and application of Environmental Impact Assessments and regular environmental monitoring can help provide the information needed for effective environmental management measures targeting individual farms, farm clusters, or a given sector producing a particular commodity, for example, shrimp, salmon, mussels, etc.
Given that particular attention should be given to the collection of wild seeds, there continues to be significant scope for the development and improvement of hatchery techniques and broodstrock management, and related application of genetic and biotechnological methods, for safe reproduction and supply of aquaculture seeds.
Generally, improved husbandry is very important, and better on-farm practices are required, particularly with regard to the selection and use of feeds and fertilizers, and the safe and effective application of drugs and chemicals. Very often there are significant opportunities to better manage the water resources utilized as well as the wastes generated. Better use of available resources, emphasizing technical and economic efficiency, will help improve farm management. Particular attention should be given to large-scale, intensive, high-input systems.
Different qualities of cultured shrimp - the smallest is diseased
More intensive production systems actually can help reducing environmental and resource use problems. For example, extensive systems require large areas (space) of land (or water), potentially contributing to degradation of habitat in some areas. More intensive systems require less area, and can be more efficient in terms of resource use and production. A good example is shrimp farming: the majority of shrimp farms are extensive or semi-intensive, and the highly publicized problems of wetland degradation are often associated with extensive systems. Intensive systems obviously may create pollution problems due to high inputs and high outputs (wastes), but this very much depends on the very site-specific characteristics of a given location, and, in particular, of the assimilative or environmental capacity of the recipient water body. In practice, effectiveness of measures and efficiency in management at the production level may well be very important criteria for consideration.
Above issues have been recognized in the past, and significant information on environmental interactions of aquaculture is available or continues to be generated. A number of conferences, expert workshops and policy meetings, have been held to address the issues, and to develop technical guidelines and policy advice. Examples include:
A variety of projects have been implemented to provide assistance in the promotion of environmental assessment and management of aquaculture development. Besides technological advances, there have also been efforts to develop and improve legal and institutional frameworks in support of sustainable aquaculture. Increasingly, there are also initiatives by associations and organizations of the private aquaculture sector aiming at improved environmental performance and better public image.
Development and improvement of legal and institutional frameworks will continue, but issues of enforcement and monitoring of compliance with environmental regulations, especially requirements for EIA and regular environmental monitoring, are still to be addressed in many countries.
Planning and management for environmentally-sustainable development of aquaculture will continue to require a substantial input of expertise in environmental assessment and management, including land and water use management, participatory consensus-building involving environmental and consumer advocacy groups and private sector representation, and policy development, based on analyses of institutional, economic and market issues.
National as well as international private sector associations and organizations involving aquaculture producers, but sometimes also suppliers, retailers, etc, are developing, with common interests focussing on specific commodities, or markets. There are private sector initiatives promoting the development of self-regulatory voluntary codes of practice, guidelines for good or best practices, etc. These private sector groups are promoting better environmental performance within their respective sectors and membership, often with a view to improve public perception of their profession, and to diversify opportunities for marketing their products.
There are trends of focusing environmental management measures on the performance of the farming process itself, which aim to reduce the generation and release of wastes, especially in form of effluent loadings, sludge, deposits, potentially harmful substances. While these efforts are extremely important, it is likely that in future calls will be growing for environmental assessment and monitoring of outcomes or effectiveness of the measures taken, i.e. the need to show that the measures put in place actually did have a tangible effect in the environment. Environmental indicators reflecting the actual ecological response (for example, by habitats, communities or populations) will likely be considered more regularly to achieve the environmental quality objectives set.
Issues of food safety of aquaculture products, which concern public health authorities and affect consumer acceptance in general, are receiving growing attention. It can be expected that there will be increasing concerns wit regard to issues of environmental impacts by aquaculture farms affecting the products of neighbouring farms, self-pollution, and environmental impacts by non-aquaculturists affecting the quality and safety of both aquaculture products as well as of aquaculture supplies, especially feeds and feed ingredients.