Like agriculture, aquaculture has also various dimensions and scales of operation. Rural aquaculture is basically a rural food farming activity which is highly compatible with other food farming components of the family level farming system. On the other hand, highly commercialized, high inputs based intensive culture of high valued finfish and shell fish is another dimension of aquaculture. Besides, there are also several intermediate levels and scales of operations.
Recent developments in the field of aquaculture, especially culture of high valued species like shrimp has brought aquaculture under the focus of attention of the people in general and the entrepreneurs and exporters in particular. The development of shrimp culture during the past 10-15 years have attracted non-farming communities and created mass awareness among the people about the potential of aquaculture for earning livelihood and for generating cash surplus. Our immediate concern, however, is to promote the type of aquaculture that is widely accepted as a potential tool for ensuring food security and generation of gainful employment opportunities in the rural areas. As indicated before world aquaculture production is dominated by small scale farmers through farming of low valued species.
Depending upon the level of intensification and extent of inputs used aquaculture practices are broadly categorized here under (Table 1).
Extensive culture systems depends largely on single input, the seed. No other extraneous material inputs are used and consequently such systems heavily depend upon the natural feed produced in the system or brought in by water in-flow. Extensive rice fish culture, culture based fisheries in ox-bow lakes and small seasonal reservoirs, shrimp/fish culture in rice fields of Kerala and bheries (large impounded shallow water areas with facilities for drawing tidal water) of West Bengal, India and fish culture in seasonal tanks of Sri Lanka are common examples of such systems.
Semi-intensive culture systems, on the other hand, also depend largely on natural food produced in-situ. However, the production of natural food is enhanced by application of organic or inorganic manure or combination of both. At this level, the practices are known as low-cost semi-intensive system. Further intensification in these systems are attained by increasing the stocking density and application of commercially available or farm made feed or locally available agricultural byproducts like bran of rice, wheat, maize etc., and various types of vegetable de-oiled cakes as supplementary feed. In semi-intensive feed and manure based freshwater carp culture, feed alone amounts to 60-70% of the total production cost. As a result, feed based culture of low valued fish species have limited acceptance among the resource poor farming communities. Low cost semi-intensive systems are followed extensively in small undrainable family ponds and relatively larger community ponds, pens erected in lakes etc. These are closely integrated component of the family farming system being practised by the majority of Asian rural communities. The integration becomes more visible when livestock housings are brought closer to the aquaculture facilities or the livestock animals are housed over or near the pond. The water is not only used for aquaculture but also for irrigation of crops, husbandry of livestock and other domestic purposes. Again, the wastes and by-products from crop/horticulture and excreta from livestock farming activities are efficiently recycled in the aquatic ecosystem in the form of high valued protein rich food. It happens in any way, whether the farming components are closely sited or kept apart (e.g. Integrated fish farming system in China).
Seasonal tanks are perhaps one of the potential resources for promoting rural development in Sri Lanka as the undrainable homestead ponds of Bangladesh, India, Vietnam and many other Low Income Food Deficit Countries (LIFDCs) of Asia. Due to its seasonal nature, most of the desired pre-stocking management measures are automatically completed. The area is dried and the bottom is exposed to the sun light which helps in disinfecting the tank. Subsequently, the area get automatically manured by the grazing cattle population that helps in the production of natural fish food in the tanks once they are filled with water. The only and the most critical input required is the desired size and species of fingerlings. The success of fish culture in these seasonal tanks will depend exclusively on the timely availability of quality fingerlings(Kumar and Pushpakumar, 1998).
Intensive culture systems are high inputs - high output based systems which require infrastructure facilities, large investment and adequate managerial skill. Such systems depend largely on complete and commercially available feed, oxygenation of the system, exchange or circulation of water etc. These culture systems are followed by corporate sector or commercial scale farmers and entrepreneurs. Such systems indirectly benefit the rural communities by creating limited job opportunities at farm level and through development of ancillary industries.
Culture of fish in cages is a technically feasible proposition but due to heavy dependence on feed, success of an operation depends largely on the cost of feed used and the market price of the produce. Seed, feed, organic and inorganic manures, lime, piscicide and certain common fish therapeutics are the usual material inputs which are required for aquaculture. The list of requirements becomes shorter when relatively low cost aquaculture is attempted. Feed is considered as the most expensive input required for semi-intensive and intensive type of aquaculture systems.
It has been repeatedly demonstrated that even at the subsistence level, aquaculture brings sizable cash income to the family besides providing fresh fish for domestic consumption. Experience gained from pilot scale interventions in several countries in Asia clearly indicate that resource poor farmers usually opt for low cost or organic manure based low-input aquaculture systems. Subsequently, by gaining confidence and experience, they gradually switch over to organic manure, inorganic fertilizer and feed based semi-intensive culture systems. Availability of a large number of economically viable culture technologies with various levels of inputs and intensification, aquaculture provides opportunities for landless, resource poor as well as well off rural communities to embark upon aquaculture for food production and income generation.
In view of the actual and potential contribution of extensive and semi-intensive aquaculture systems in providing increased availability of cheap animal protein to the traditionally rice and fish eating rural population of Asia, and supplementing family income through sale of domestic surplus, some of the countries in the region such as India, Bangladesh, Vietnam, Laos, China, etc. have accepted aquaculture as one of the components of their Integrated Rural Development Programme (IRDP). As a component of the family farming system, it helps in product diversification and spreading risk.
Table 1. Aquaculture systems based on levels of intensification and inputs use
|
Intensification levels |
Major inputs |
Some common examples |
|
Extensive culture systems |
Seed from adjoining natural source or hatchery produced or
from both |
|
|
Semi-intensive culture systems
|
Seed manure Lime Piscicide (once in several years for perennial ponds and only when drying is not possible) Seed Organic and inorganic manuresFeed (mostly farm made /
compounded) Lime Fuel or electricity for dewatering perennial ponds or piscicide
when drying is not possible Common therapeutants |
|
|
Intensive culture systems |
Seed Feed (mostly pelleted and commercially available) Lime /
dolomite Piscicide Energy (electricity / gasoline) Water(exchange /
recirculation) Oxygen (aeration) Therapeutant High level of management |
|
