|Aquaculture - Initial Environmental Assessment Series No. 5 (NORAD, 1992)|
|Part I: General account|
Aquaculture entails controlled farming or cultivation of organisms in salt, brackish or fresh water for the purpose of food production. Aquaculture produce is also put to good use in other connections, e.g. pharmaceutical or cosmetic industries.
This booklet for initial environmental assessment covers aquaculture projects consisting of farming/cultivation and harvesting of fish, shellfish, molluscs (shells, snails) or seaweeds. Farming of crocodiles and turtles are also forms of aquaculture, but will not be dealt with in this booklet. In addition to the aquaculture farm as such, a project may include facilities for the production of fry and feed. Some aquaculture projects may also require facilities for the processing and distribution of the aquaculture products. These can be separate projects or sub-projects of a major aquacultural investment. Aquacultural investment may also entail measures in terms of training, research, legislation, consulting, marketing, administration and establishment of institutions.
The choice of technology, scale and intensity of cultivation will vary a great deal, and will be decisive for the environmental and socio-cultural impacts of aquaculture. Aquaculture projects may vary as to stocking of organisms, preparation of the production areas and the degree of feeding, fertilization and medication. The farm organisms can be restocked at different stages of development. For example, they may be wild fry which have been collected for further cultivation. In other cases the fry are farm-cultivated. Import of fry from other districts or countries is another alternative. Preparing the production areas may involve making enclosures in bays, lagoons, lakes, ponds or man-made ponds/reservoirs, the building of artificial embankments and basins, and the use of cages. A cage is an open, free floating net attached to a framework for use in both freshwater and saltwater environments (cf. chapter 2).
It is common to distinguish between extensive, semi-intensive and intensive production, depending on the degree of feeding and fertilization in the farms. Extensive farming involves no feeding and no, or minimal, fertilization, semi-intensive some supplementary feeding and fertilization, and intensive steady supply of feed and fertilizers. The more intensive the production, the higher is the density of farm organisms in the farming medium. In intensive farming systems, aimed at a high production, the density of farm organisms is often very high. Moreover, intensive systems are based on the cultivation of only one species (monoculture). The environment therefore becomes very different from a natural one, and the farm organisms may be exposed to stress and a greater susceptibility to diseases. Accordingly, the need for medication will increase in proportion to the degree of intensification. In extensive and semi-intensive farming there will rarely be a need for medication, whereas drugs such as antibiotics, fungicides and parasiticides are necessary in intensive systems.
In developing countries there are intensive, semi-intensive as well as extensive farming systems. Extensive and semi-intensive systems are currently the most common. In several places, however, there is growing interest in the development of intensive systems. Generally speaking, extensive and semi-intensive aquaculture can be said to be more easily adaptable to a particular environment, and the potential environmental problems will be fewer and less serious than those caused by intensive aquaculture.
Extensive and semi-intensive farming systems are often technically simple, but can at the same time be biologically complicated. Several species are often cultivated simultaneously (polyculture), exploiting different ecological niches. In the countryside semi-intensive systems often combine agriculture and aquaculture. In this way agricultural refuse, manure from domestic animals etc. are utilized in fish-pond production. Fish farming can also be based on other supplies of nutrients such as sewage and septic waste. Extensive and semi-intensive systems are generally labour-saving and less capital-intensive, many have been operated for several generations and are well adjusted to local conditions. The development of extensive and semi-intensive systems is commonly geared towards production for local consumption. Generally, therefore, no major development of processing and distribution systems is required.
The cultivation of molluscs and seaweeds takes place extensively. Molluscs, for example, will take advantage of the local production facilities by filtering particles from the waters. Such a farm may therefore, to a certain extent, serve as a purifier plant, as the shells filter small organic particles. The organisms to be cultivated are restocked or planted, for example on devices where the organisms can fasten themselves.
Historically intensive farming systems are relatively young. They have been in the process of development since the turn of the century, but have received a powerful impetus in the last decades. Primarily it is carnivorous (carnivore) species of fish and shellfish that are being cultivated intensively.
The requirements as to control and management of the feeding, medication, water quality and volume are higher than those applying to other systems. Further, the hygienic requirements are high, since the risk of pollution from drugs, nutrients and organic matter is high. Regular maintenance and cleaning of the farms is necessary. Intensive farming often requires a considerable capital investment and the availability of a trained and permanently employed workforce. Nevertheless, the forms of farming are not especially labour-intensive. They often involve a great increase in production and will generally require the establishment of facilities for reception, processing and distribution of the farm products.
The development of a reception, processing and distribution apparatus for aquaculture production requires land and a stable supply of energy (oil and electricity) and high-quality water. This especially applies to modern methods of preservation such as icing and freezing, but traditional methods of treatment, e.g. smoking, also depend on an ensured supply of energy. Less energy-consuming methods, e.g. drying and salting, may be relevant alternatives. An increased investment in aquaculture, moreover, requires a sufficient supply of building materials, e.g. wood for the building of cages or pens.
The handling of large amounts of farm products in a restricted area can cause problems with the treatment of waste (cf. the booklet for initial environmental assessment of waste treatment and disposal). Waste from e.g. the handling and processing of fish consists of easily decomposable organic matter which accounts for between 5 and 30 per cent, and in special cases up to 70 per cent, of the raw material, depending on the degree of processing. This waste is actually a resource which may yield a series of valuable products, e.g. feed, fish meal, fish oil, big-gas, fertilizers etc., or form a basis for the production of more specialized organic products.
As already mentioned, a major development of aquaculture is likely to lead to the development of several associated functions. In such cases, one can also consult the checklists and/or booklets for initial environmental assessment of industry, transport, development of densely populated or urban areas etc..
If the aquaculture project comprises training and/or the development of administration and institutions, environmental aspects and the question of environmental competence should be given careful consideration.