8.5 Implementation and Evaluation of the Modified Pond
Management System
A modified, semi-intensive polyculture system centered on common carp was
designed, based on an investigation carried out into the traditional aquaculture
system used by the Black Thai farmers (Steinbronn 2009), a determination of the
nutritional value of local resources such as fish feeds (Dongmeza 2009) and the
formulation of cost efficient supplemental feeds for common carp, made mainly
from locally available resources (Tuan 2010).
8.5.1 Implementation of the Modified Pond Management System
The system was tested under field conditions in the Black Thai farmers’ ponds in
the research area (Pucher et al. 2010a, b). The main modifications made are listed in
Table 8.4 and are described in the following section.
For reasons of pond hygiene, systematic aquaculture pond preparation practices
had to be introduced. Steinbronn (2009) described the traditional Black Thai
farmers’ aquaculture as a pond management system with irregular catch and stocking processes. Farmers caught low value fish for household consumption, wherein
stocking times and harvesting of the ponds were dependent on the current workload
and financial situation, and number of fingerlings provided by the traders. Complete
harvests were performed rarely and only a few farmers drained all the water from
their ponds. Consequently, farmers did not know the species’ composition, stocking
density or survival rate of the fish in their ponds. Both the gross accumulation of
organic material and the sedimentation of particles derived from the eroded soils
were frequently observed and reported by farmers in the research area. Under the
modified pond management system, researchers recommended that farmers
completely drain the ponds after each production cycle, plus remove accumulated
sediments and indigestible feed fractions in order to reduce anaerobic bacterial
activity (Sugita et al. 1992), as well as reduce oxygen consumption through decomposition (Barik et al. 2000), especially that caused by the intensive culture of grass
carp. The ponds’ bottoms then had to be dried out and quick-lime applied.
For the implementation of this semi-intensive pond aquaculture system, several
structural modifications to the ponds were recommended. In the traditional ponds
used in northern Vietnam, water from all neighboring water sources (channels, rice
paddies and ponds) flows into the ponds without any control, either over the water
which flows through openings specially created for the purpose, or over water
flowing in passively through cracks and holes in the dikes (Reinhardt et al. 2012),
or even as run-off from surrounding gardens, fields and forests. Tuan et al. (2010)
reported a yearly run-off of 2.5 % of precipitation for the period May 2009 to April
2010, and an average transport of 6.6 kg (minimum 2.1 kg to maximum 13.2 kg)
eroded soil per m
2 per year for upland maize fields, with especially high erosion
8 Improved Sustainable Aquaculture Systems for Small-Scale Farmers . . .
295
Management System
A modified, semi-intensive polyculture system centered on common carp was
designed, based on an investigation carried out into the traditional aquaculture
system used by the Black Thai farmers (Steinbronn 2009), a determination of the
nutritional value of local resources such as fish feeds (Dongmeza 2009) and the
formulation of cost efficient supplemental feeds for common carp, made mainly
from locally available resources (Tuan 2010).
8.5.1 Implementation of the Modified Pond Management System
The system was tested under field conditions in the Black Thai farmers’ ponds in
the research area (Pucher et al. 2010a, b). The main modifications made are listed in
Table 8.4 and are described in the following section.
For reasons of pond hygiene, systematic aquaculture pond preparation practices
had to be introduced. Steinbronn (2009) described the traditional Black Thai
farmers’ aquaculture as a pond management system with irregular catch and stocking processes. Farmers caught low value fish for household consumption, wherein
stocking times and harvesting of the ponds were dependent on the current workload
and financial situation, and number of fingerlings provided by the traders. Complete
harvests were performed rarely and only a few farmers drained all the water from
their ponds. Consequently, farmers did not know the species’ composition, stocking
density or survival rate of the fish in their ponds. Both the gross accumulation of
organic material and the sedimentation of particles derived from the eroded soils
were frequently observed and reported by farmers in the research area. Under the
modified pond management system, researchers recommended that farmers
completely drain the ponds after each production cycle, plus remove accumulated
sediments and indigestible feed fractions in order to reduce anaerobic bacterial
activity (Sugita et al. 1992), as well as reduce oxygen consumption through decomposition (Barik et al. 2000), especially that caused by the intensive culture of grass
carp. The ponds’ bottoms then had to be dried out and quick-lime applied.
For the implementation of this semi-intensive pond aquaculture system, several
structural modifications to the ponds were recommended. In the traditional ponds
used in northern Vietnam, water from all neighboring water sources (channels, rice
paddies and ponds) flows into the ponds without any control, either over the water
which flows through openings specially created for the purpose, or over water
flowing in passively through cracks and holes in the dikes (Reinhardt et al. 2012),
or even as run-off from surrounding gardens, fields and forests. Tuan et al. (2010)
reported a yearly run-off of 2.5 % of precipitation for the period May 2009 to April
2010, and an average transport of 6.6 kg (minimum 2.1 kg to maximum 13.2 kg)
eroded soil per m
2 per year for upland maize fields, with especially high erosion
8 Improved Sustainable Aquaculture Systems for Small-Scale Farmers . . .
295