the case of high protein feed ingredients, and the high protein feed ingredients used
in these trials were heated soybean meal and fishmeal. However, to date, the
availability of these ingredients has been limited in the research area, as it has
across the marginal uplands, so there has been little demand. Even though
Vietnamese markets are known to react rapidly to changing conditions, the demand
for these resources will probably remain low in the future, because these feed
ingredients are relatively costly in the local market and globally. Therefore, farmers
are unlikely to invest in this fishmeal based fish feed, even though it would be to
their net benefit. In the meantime, it is more than likely that competition for
fishmeal will increase over time, both in Vietnam and worldwide, and prices will
thus rise still further as fishmeal becomes a limited resource. To avoid fishmeal
expenses, the use of earthworms is a promising alternative. The study here showed
that an average household of Black Thai farmers in the research area produces
enough organic waste to consider earthworms as a replacement for fishmeal in
terms of supplemental feed (Mu ¨ller et al. 2012). Earthworm meal was shown to be
able to partly replace fishmeal in the diets of common carp under laboratory
conditions (Tuan and Focken 2009), while under pond conditions, no significant
difference was found between the performance of fish diets containing fishmeal or
those containing earthworm meal, due to the simultaneous consumption of pond
products such as zooplankton and zoobenthos (Pucher et al. 2012b). Further
research is needed; however, in order to consider making technical modifications
to the vermiculture techniques used, such as improving the worm harvest, developing optimal techniques for the use of worms in aqua-feeds, and carrying out
investigations into the alternative on-farm organic materials that could be used.
Fertilization using organic and inorganic fertilizer in static water requires the use
of an optimal fertilizing scheme to help reduce the risk of nutrient accumulation
in the sediments and of algae mass blooms and algae mass die-offs occurring.
A precautionary fertilizing scheme adapted to local soil, climate and water
conditions is needed for diluting pond water in cases of emergency, especially in
areas with limited water resources.
Another possible innovation relates to the supply of common carp for stocking
the fish ponds. Currently, common carp partly originate from hatcheries and partly
from spontaneous reproduction within the fish ponds. Spontaneous reproduction of
common carp and tilapia is unpredictable in terms of timing and outcomes; therefore, farmers have little advance information on their fish stocks and fish may be
rather small at the end of the annual growing season, resulting in high mortality
rates during the cold months. Some farmers could produce common carp fry on
their own, by adapting the system of spawning ponds (Dubisch ponds) practiced in
Europe for more than a century. This would allow the local production of common
carp fry and fingerlings, and thereby, help farmers to stock their ponds according
to their own demands; not governed by the erratic supply provided by the traders.
By supplying farmers with good, virus-free brood stock, such decentralized fry
production techniques could help to avoid the spread of CyHV that occurs when
using the provincial hatcheries (see Sect. 8.5).
310
J. Pucher et al.
in these trials were heated soybean meal and fishmeal. However, to date, the
availability of these ingredients has been limited in the research area, as it has
across the marginal uplands, so there has been little demand. Even though
Vietnamese markets are known to react rapidly to changing conditions, the demand
for these resources will probably remain low in the future, because these feed
ingredients are relatively costly in the local market and globally. Therefore, farmers
are unlikely to invest in this fishmeal based fish feed, even though it would be to
their net benefit. In the meantime, it is more than likely that competition for
fishmeal will increase over time, both in Vietnam and worldwide, and prices will
thus rise still further as fishmeal becomes a limited resource. To avoid fishmeal
expenses, the use of earthworms is a promising alternative. The study here showed
that an average household of Black Thai farmers in the research area produces
enough organic waste to consider earthworms as a replacement for fishmeal in
terms of supplemental feed (Mu ¨ller et al. 2012). Earthworm meal was shown to be
able to partly replace fishmeal in the diets of common carp under laboratory
conditions (Tuan and Focken 2009), while under pond conditions, no significant
difference was found between the performance of fish diets containing fishmeal or
those containing earthworm meal, due to the simultaneous consumption of pond
products such as zooplankton and zoobenthos (Pucher et al. 2012b). Further
research is needed; however, in order to consider making technical modifications
to the vermiculture techniques used, such as improving the worm harvest, developing optimal techniques for the use of worms in aqua-feeds, and carrying out
investigations into the alternative on-farm organic materials that could be used.
Fertilization using organic and inorganic fertilizer in static water requires the use
of an optimal fertilizing scheme to help reduce the risk of nutrient accumulation
in the sediments and of algae mass blooms and algae mass die-offs occurring.
A precautionary fertilizing scheme adapted to local soil, climate and water
conditions is needed for diluting pond water in cases of emergency, especially in
areas with limited water resources.
Another possible innovation relates to the supply of common carp for stocking
the fish ponds. Currently, common carp partly originate from hatcheries and partly
from spontaneous reproduction within the fish ponds. Spontaneous reproduction of
common carp and tilapia is unpredictable in terms of timing and outcomes; therefore, farmers have little advance information on their fish stocks and fish may be
rather small at the end of the annual growing season, resulting in high mortality
rates during the cold months. Some farmers could produce common carp fry on
their own, by adapting the system of spawning ponds (Dubisch ponds) practiced in
Europe for more than a century. This would allow the local production of common
carp fry and fingerlings, and thereby, help farmers to stock their ponds according
to their own demands; not governed by the erratic supply provided by the traders.
By supplying farmers with good, virus-free brood stock, such decentralized fry
production techniques could help to avoid the spread of CyHV that occurs when
using the provincial hatcheries (see Sect. 8.5).
310
J. Pucher et al.