Environmental Concerns
As air breathers, walking catfish
can be grown at extremely high density,
with standing crops in pond culture
reaching 100 mt/ha. Waste feed
and metabolites often cause poor
water quality and heavy phytoplankton
blooms throughout most of the
growout period. To maintain tolerable
water quality for fish growth,
pond water is often exchanged during
later stages of the culture cycle.
Discharge of waste water from
walking catfish ponds has become a serious
issue, especially in northeast
Thailand, where surface waters are in
short supply. Farmers often discharge
waste water to adjacent rice fields,
which can be damaged by the unbalanced
nitrogen:phosphorus ratios.
Integrated recycling systems are
being developed to recycle nutrients
in the catfish wastes as fertilizers to
stimulate natural food production for
filter-feeding species such as Nile
tilapia, Oreochromis niloticus. These
systems include cage-cum-pond and
pen-cum-pond approaches suitable
for small-scale farmers. Some farmers
also use catfish waste water to culture
Nile tilapia and giant Mekong
catfish, Pangasius gigas.