in conjunction with a modified pond management system, was tested in field trials
in collaboration with the Yen Chau farmers (Pucher et al. 2010a). The results of
these trials are presented in Sect. 8.5.
The use of earthworms as a fish feed ingredient has also been found to be a
practicable alternative for farmers. Earthworms have high protein content (71 % of
DM) and can contribute to a significantly improved growth rate in common carp
(Tuan 2010; Pucher et al. 2012b). The use of earthworms is discussed in Sect. 8.8.
8.4 Design of an Improved Aquaculture System for Small-Scale
Farmers
Based on the above analysis of the problems and limitations experienced within the
aquaculture system currently practiced by the Black Thai farmers in Yen Chau
district, and the possibilities outlined, an improved system was designed. The goals
of this system were to reduce the cultural dependency on the use of disease-prone
grass carp, and to increase income generated from fish culture without reducing the
contribution of the pond system to household protein supply. The only species that
can catch and even exceed prices on the market similar to those obtained for grass
carp is the common carp (Steinbronn 2009). The common carp is reared in many
tropical, subtropical and temperate zone countries around the globe, predominantly
in semi-intensive systems. In these systems, natural food is enhanced by fertilization and/or liming of the pond, and the natural food is supplemented by feeds
typically lower in protein content than the physiological requirements of the fish
(De Silva 1995), making the fish feed cheaper for balanced diets (Hepher and
Pruginin 1981). Farmers in Yen Chau area have available a number of potential
feed ingredients from other farming activities, such as rice bran and maize; however, in order to achieve efficient fish production levels with such a low-cost feed,
natural food from the pond must supply sufficient protein and essential micronutrients. This can only be achieved in ponds with controlled water exchange,
which is done to avoid the washing-out of nutrients supplied in the form of organic
or inorganic fertilizers. Such nutrient-rich ponds also provide a suitable environment for tilapia and small, self-recruiting fish, mollusks and crustacean species to
grow, which then contribute to home consumption. Therefore, the suggested set of
innovations are to control water flow through the fish pond by uncoupling the pond
from the irrigation systems, to dig canals around the pond in order to catch run-off
water from the adjacent upland areas, apply lime, organic (manure) and inorganic
fertilizers, modify the species composition of the fishpond – with fewer grass carp
and more common carp, and apply supplemental feeds at least partly based on onfarm or locally available resources.
294
J. Pucher et al.
in collaboration with the Yen Chau farmers (Pucher et al. 2010a). The results of
these trials are presented in Sect. 8.5.
The use of earthworms as a fish feed ingredient has also been found to be a
practicable alternative for farmers. Earthworms have high protein content (71 % of
DM) and can contribute to a significantly improved growth rate in common carp
(Tuan 2010; Pucher et al. 2012b). The use of earthworms is discussed in Sect. 8.8.
8.4 Design of an Improved Aquaculture System for Small-Scale
Farmers
Based on the above analysis of the problems and limitations experienced within the
aquaculture system currently practiced by the Black Thai farmers in Yen Chau
district, and the possibilities outlined, an improved system was designed. The goals
of this system were to reduce the cultural dependency on the use of disease-prone
grass carp, and to increase income generated from fish culture without reducing the
contribution of the pond system to household protein supply. The only species that
can catch and even exceed prices on the market similar to those obtained for grass
carp is the common carp (Steinbronn 2009). The common carp is reared in many
tropical, subtropical and temperate zone countries around the globe, predominantly
in semi-intensive systems. In these systems, natural food is enhanced by fertilization and/or liming of the pond, and the natural food is supplemented by feeds
typically lower in protein content than the physiological requirements of the fish
(De Silva 1995), making the fish feed cheaper for balanced diets (Hepher and
Pruginin 1981). Farmers in Yen Chau area have available a number of potential
feed ingredients from other farming activities, such as rice bran and maize; however, in order to achieve efficient fish production levels with such a low-cost feed,
natural food from the pond must supply sufficient protein and essential micronutrients. This can only be achieved in ponds with controlled water exchange,
which is done to avoid the washing-out of nutrients supplied in the form of organic
or inorganic fertilizers. Such nutrient-rich ponds also provide a suitable environment for tilapia and small, self-recruiting fish, mollusks and crustacean species to
grow, which then contribute to home consumption. Therefore, the suggested set of
innovations are to control water flow through the fish pond by uncoupling the pond
from the irrigation systems, to dig canals around the pond in order to catch run-off
water from the adjacent upland areas, apply lime, organic (manure) and inorganic
fertilizers, modify the species composition of the fishpond – with fewer grass carp
and more common carp, and apply supplemental feeds at least partly based on onfarm or locally available resources.
294
J. Pucher et al.