Browsing by Subject "Carp polyculture"

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A case study: Fish production in the integrated farming system of the Black Thai in Yen Chau district (Son La province) in mountainous North-western Vietnam - current state and potential
(2009) Steinbronn, Silke; Becker, Klaus
Son La province is located in mountainous north-western Vietnam and belongs to the poorest regions of the country. In the valleys of this province, fish farming is one of the major activities among farmers who belong to the ethnic Black Thai minority. Up until now, the aquaculture system practiced here has not been scientifically investigated. There is generally very little data available regarding the aquaculture of resource-poor farmers in Southeast Asia. This lack of information can be partly explained by the difficulty in obtaining this data. However, a solid understanding of current aquaculture systems is necessary for any kind of future involvement. Within the course of a special research program (SFB 564), aquaculture practices in three communes of Yen Chau district (Son La province) were surveyed between 2004 and 2006. The research was conducted in a holistic way in order to obtain a detailed description of the typical local aquaculture system with its potentials and limitations. In addition, measures for improvement were developed, which will be tested during the next phase of the special research program. The data was collected and analyzed on three different levels. On the ?macro level?, general data is presented regarding the land use and irrigation system in the studied area. Data on the ?meso level? concerns the aquaculture and agriculture system and was predominantly collected through interviews with 155 farmers, 22 village headmen and other stakeholders. On the ?micro level?, an in-depth investigation based on measurements and close observation of 6 individually selected case study farms is presented. This data includes the limnological pond conditions, fish growth rates, food conversion and the profitability of the aquaculture system. The data gathered during these investigations compensates for the information that could not be satisfactorily gathered through the interviews alone. Currently, around 63% of the households in the study area produce fish in ponds. The aquaculture production is closely linked with other farming activities and is integrated into the overall irrigation system. Farmers stock different carp and tilapia in polyculture with the main species being grass carp. Fish are mainly fed leaves and by-products of crop production, weeds and manure, e.g. from buffalo. The pond system is feed-based and exhibits a more or less continuous water flow; both of these features are rather atypical for small-scale aquaculture. In the case study farms, the average fish stocking density was 1.0 fish m-2. Calculated based on one hectare, the average daily feed application was 37.1 kg dry matter (DM) and the annual net production of aquatic species 1.5 tons ha-1, of which roughly 2/3 were sold. The average conversion of feed (DM) to aquatic species biomass was 7.7:1, and the conversion of added nitrogen (feed and manure) to produced nitrogen (aquatic species) was 14.7%. The yields in the presented system are relatively low compared to other feed-based aquaculture systems. Nevertheless, it has been shown that aquaculture production contributes significantly to food security, generates income and plays a significant role in farmers? lives. At present, the local market in Yen Chau cannot be completely satisfied by the districts? fish production alone. Recently, a road was upgraded that connects the north-western mountains with the country?s capital Hanoi. As a result, fish from the more intensive aquaculture in the lowlands has started to flood the local markets. This development is expected to proceed, which will leave farmers unable to compete in the market in the future. In order to produce fish in a sustainable way, the current system must be improved so that the local fish production increases. There are various reasons that can explain the relatively low productivity in the ponds. These include an unclassifiable grass carp disease that leads to high mortalities, poor water quality, low fish growth rates caused by low quality of fish seed, low quality of feed and manure applied as well as low natural food availability in the ponds. Furthermore, farmers seem to have limited knowledge regarding basic aquaculture techniques, which may be explained by the lack of training or extension services available in this field. In the present study, a ?basket? of modification measures have been proposed. These measures concern the farms themselves (e.g. improved pond management), the institutional and political framework (e.g. support of the local hatcheries) as well as the research. The focus of the next part of the special research program will be the identification of the causative agent of the grass carp disease and the development of prevention and treatment strategies. Additionally, a modified watering and feeding management system will be tested scientifically. It is expected that this locally adapted, improved pond system will lead to significantly higher fish production.