Abstract
Small-scale aquaculture in Cambodia is expanding rapidly and contributing immensely to improved food security of people in rural areas. Though the country has no tradition of pond aquaculture and is dependent largely on capture fisheries to meet the fish needs of people, increasing population pressure has encouraged farmers to explore aquaculture as an additional occupation in the farming system. Initially farmers attempted to culture tilapia but poor knowledge of aquaculture resulted in disappointing experience for the farmers. Strategic intervention by the OXFAM group of NGOs through the Department of Fisheries encouraged farmers to explore aquaculture as an option with the required technical support. Farmer participatory research approaches were used to develop aquaculture technologies appropriate for small farmers in Cambodia involving carps, catfish and tilapia with species combinations ranging from two to seven species. Common carp (Cyprinus carpio), silver barb (Barbodes gonionotus) and Nile tilapia (Oreochromis niloticus) is a popular combination with farmers with a stocking ratio of 3:4:3. In addition to these species, farmers combine other species such as silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis) and silver striped catfish (Pangasius hypophthalmus) with silver barb, silver carp or Nile tilapia used as dominant species at 35-40% and the other species stocked in the range of 5-20% each. Though catfish survives and grows well, because of its high feed demand, farmers are advised to stock this species only at 5-10%. A problem of muddy water commonly encountered in most parts of the country has been overcome through the application of lime, fertilizers and green manure up to 30-40 kg 100 m-2 as an initial dose. The quantity could even be doubled when the organic matter content is low in pond soils, particularly in new ponds. The green water technology concept appropriate for small farmers is promoted with most species cultured capable of efficiently harvesting the natural food produced in the system. Farmers are advised to keep the water green through regular application of organic manures and inorganic fertilizers and by keeping a constant watch on the colour of the water. Fish are stocked in the range of 2-5 fish m-2 and are fed with variety of natural feed resources available like Azolla, Lemna and Wolfia. Among animal resources earthworms, slaughter house wastes and termites are provided. Rice bran is the most common feed input provided by all farmers throughout the year. Impressive production ranging from 30-40 kg 100 m-2 and even up to 100 kg m-2 has been obtained by farmers. Women's participation in aquaculture increased innovations and sustainability of the activity. Farmer-based extension has proved to be successful in the area and people have taken up fish culture as an additional income generating activity. Enterprising farmers have resorted to local production of fish seed by establishing small-scale hatcheries and nursing fish seed as economic activities. This has helped farmers to obtain quality seed in the local area without depending on outside sources for seed and knowledge.
Effect of dietary carbohydrate to lipid ratio on performance of Nile tilapia and enhancement of natural food in pond aquaculture
