\
Concluding remarks
409
Problems
of
water
pollution
may
occur
when carp
or
other
species are
intensively
reared in
cages on pelleted foods
which generate
faecal and
waste
food nutrient loadings.
This
should be avoidable since We
know the capacity of
well managed water bodies to receive wastes and yet maintain good water quality.
Carp intensively bred in cages
are
equivalent to intensively reared pige or ducks
and their detritus could be recycled in the same manner (Bieniarz, Avime1ech).
Among the
technical problems
raised, larval and fry rearing in
ponds was
discussed.
The
time and size at
which larvae and fry should
be released
into
nursery or growing ponds is critical.
The environment should be free of predators
andparasites or, if these are present, the released young must be large enough to
resist
them.
A
large
variety
of
and—predator techniques
and
devices
were
mentioned:
inlet water ltration increasing salinity, fenc_ing around or Spreading
nets over the pond to
prevent tadpole and
bird
access
etc. (Tennakoon, Salman,
0 pus zinski).
The need for better scientific knowledge was emphasised; particularly better
understanding
of
fish
behavi0ur
(feeding
behaviour, social interactions
in
polyculture etc.) and of pond ecosystems.
This would allow better management of
the
cultured
fish
populations and
of
the. food‘clhain‘s upon which they depend.
Among other
research directions, the mechanisms
pH
change in pond
water
(Olah, Heym an) and sulfate—sulde
and
their effects on
availability of natural detrital foods,
column acidity were
suggested.
Sulfate—sulfide
transition
produces
acidic conditions
and
sulde is
highly toxic (Schroeder).
In summary, many problems were debated. Some were conceptual; eg. besides
the well—balanced, traditional integrated sh farming using _ponds there are some
systems
for
rearing
carp and other
species in cages in owing ' waterwithout
recycling of wastes.
Other
problems
political; eg. in integrated fish farming,
sh is sometimes a byproduct and authorities with responsibility for allocation
of
water
use
rights may
face conflicts
between
water use for raising
sh or for
irrigation.
However,
most
of the
problems remain scientific
and technical m
nature, the solutions of which will only come through increased support.
_
-
R. Pullin
.
,
…
"\”MM”H\
Concluding remarks
409
Problems
of
water
pollution
may
occur
when carp
or
other
species are
intensively
reared in
cages on pelleted foods
which generate
faecal and
waste
food nutrient loadings.
This
should be avoidable since We
know the capacity of
well managed water bodies to receive wastes and yet maintain good water quality.
Carp intensively bred in cages
are
equivalent to intensively reared pige or ducks
and their detritus could be recycled in the same manner (Bieniarz, Avime1ech).
Among the
technical problems
raised, larval and fry rearing in
ponds was
discussed.
The
time and size at
which larvae and fry should
be released
into
nursery or growing ponds is critical.
The environment should be free of predators
andparasites or, if these are present, the released young must be large enough to
resist
them.
A
large
variety
of
and—predator techniques
and
devices
were
mentioned:
inlet water ltration increasing salinity, fenc_ing around or Spreading
nets over the pond to
prevent tadpole and
bird
access
etc. (Tennakoon, Salman,
0 pus zinski).
The need for better scientific knowledge was emphasised; particularly better
understanding
of
fish
behavi0ur
(feeding
behaviour, social interactions
in
polyculture etc.) and of pond ecosystems.
This would allow better management of
the
cultured
fish
populations and
of
the. food‘clhain‘s upon which they depend.
Among other
research directions, the mechanisms
pH
change in pond
water
(Olah, Heym an) and sulfate—sulde
and
their effects on
availability of natural detrital foods,
column acidity were
suggested.
Sulfate—sulfide
transition
produces
acidic conditions
and
sulde is
highly toxic (Schroeder).
In summary, many problems were debated. Some were conceptual; eg. besides
the well—balanced, traditional integrated sh farming using _ponds there are some
systems
for
rearing
carp and other
species in cages in owing ' waterwithout
recycling of wastes.
Other
problems
political; eg. in integrated fish farming,
sh is sometimes a byproduct and authorities with responsibility for allocation
of
water
use
rights may
face conflicts
between
water use for raising
sh or for
irrigation.
However,
most
of the
problems remain scientific
and technical m
nature, the solutions of which will only come through increased support.
_
-
R. Pullin
.
,
…
"\”MM”H\