Small-scale aquaculture in upland areas of Yen Chau District, Son La Province / Northern Vietnam
- Publication Type
- Contribution to conference
- Authors
- Steinbronn S., Tuan N. N., Focken U. and Becker K.
- Year of publication
- 2005
- Conference name
- Deutscher Tropentag, October 2005
- Conference location
- Stuttgart
Within the framework of the Special Research Program “Sustainable land use and rural development in mountainous regions of Southeast Asia” a survey on aquaculture practices was carried-out in Yen Chau district, Son La province (Northern Vietnam). The region is classified as poor. Depending on the village, 30 – 95% of all farmers own ponds. About 80 farmers in a perimeter of 20 kilometres around Yen Chau town operating grow-out ponds were interviewed on their farming activities. All belong to the ethnic minority of Black Thai.
Typically, the Black Thai farmers live in villages in the valleys and cultivate maize, cassava and occasionally cotton as cash crops on the hillsides. Most farmers have smaller paddy plots in the valleys. Usually, the rice is only for home consumption. Often farmers possess one or more buffalos, some farmers own cattle and pigs additionally. Many also raise chicken and ducks. Fish ponds are mostly located between the paddy fields or next to the houses of farmers. The ponds (size between 200 and 5 000 m2, most ponds below 1 000 m2) are characterized by a continuous water-flow. Usually, the farmers raise grass carp, mud carp, common carp and tilapia, in many cases also silver carp and silver barb (mean stocking density: 1 fish/m2). Around 30% of all stocked fish are grass carp. Fry or fingerlings are obtained from the local hatcheries. Tilapia and common carp are often not stocked due to natural reproduction.
The main feed inputs to the pond system are crop residues, such as banana, cassava, bamboo and maize leaves and rice bran. Different grasses and duck weed, normally collected from the paddy fields, are also fed. Almost all farmers manure their ponds with fresh manure (mainly from buffalo), but no animals are stocked in pens next to or above the pond.
The farmers usually harvest one or two years after stocking. The mean fish yield is around 240 g/m2. A significant part (up to 100 kg/year) is consumed by the household itself or used as a gift item. The remaining part is sold to traders. In Yen Chau the prices for fish at the local market are generally considered as high (~ 1 US$/kg grass carp). Prices for fish have further increased since the outbreak of bird flu in winter 2003/04. Farmers also collect snails, molluscs and shrimps from the pond. Fish farming is an important source of cash income and an essential animal protein supplement in the families’ diets.
The fish yield of roughly 240 g/m2 for a 2-year production cycle must be considered relatively low for a feed-based aquaculture system. Among the possible reasons for this are a) lack of training or extension services in the field of aquaculture, b) low quality of the stocking material, c) high mortality of grass carp due to diseases (84% farmers reported diseases of grass carp in former years) and d) negative impact of inorganic fertilizers and pesticides applied in paddy fields above the ponds.
Ongoing research aims at elucidating the nutrient flow patterns in this forage-based aquaculture system and at establishing nutrient flow models. Based on these models, improved management schemes will be developed with the purpose of increasing productivity of the aquaculture system and income of the farmers.