30
RS. V. Fall…
For
example,
in
the
tropics,
combining a
benthic
feeder
(common carp), the
vegetation consumption/Eaecal fertilization
effects of grass carp,
a
good general
'mopping
up‘
species
(like rohu)
and
opportunistic
microphagous species
(like
tilapias) would provide a
mixture of versatile species, all of which could
respond
to
various intensities of supplemental feeding and the com binations of which c0uld
be
varied according to
demand and
value.
Other
species, e.g. catla,
eculd be
added according to demand.
The interrelationships
of
auto—
and
heterotrophic
food webs
in wastefed
systems
also merit further study.
The technique
of tracing food webs by carbon
isotopes (Schroeder, 1983) is an important tool. In the tropics, there seems to be a
limit to fertilized
pond
production without supplementatal feeding
and
aeration,
allowing
higher
stocking.
Where these are
unaffordable,
greater yields
could
perhaps be obtained by better
manipulation and
enhancement
of planktonic
and
detrital food sources.
E — Diseases
Carps suffer from
many diseases, especially
when under stress from adverse
environments and poor nutrition.
Many carp microbial pathogens and parasites are
ubiquitous (e.g.., trichodinid protozoans and ectoparasitic crustaceans). Some have
been spread with fish transfers, e.g. lchthvophthirius,
Lernaea
and
Myxobolus to
Indonesia.
Disease problems are generally more serious at low temperatures and in
temperate
regions
than
in the
tropics,
apart
from
the
periodic
devastating
outbreaks of ulcerative diseases recorded in Southeast Asia
(Aeromonas spp. have
been cited as
primary pathogens,
but many secondary invaders —
bacteria, fungi
and protozoa — are
involved).
Recent trends include a stronger awareness of the
need
for stricter quarantine
procedures (IDRC, 1983),
and increasing interest
by
major
drug companies to
develop
and supply compounds
for
hatchery
hygiene,
disease prophylaxie and
chemotherapy.
Despite this and the possible development
of
vaccines
and genetic resistance
to
diseases, good husbandry, good
nutrition,
high
standards of hygiene (especially in
hateheries) remain the
cultu1‘ist's
chief
safeguard.
ACKNOWLEGEMENTS
I wish to thank all those who helped with information for the compilation of
this
review, especially, J.
Balarin,
R.
Berka,
T.
Bhukasawan, R. Billard, R.
Chilvers,
C.H. Fernando, H.F. Henderson, L. Horvath, K.H.
Ibrahim, M.R. Jaffa,
I—B. Kim, C.
Lee, Li Sifa, M.
von
Lukowicz, R.C. May, D. Mires, K. Pinter, J.
Stoneman and
W. Steffens.
REFERENCES
BBS.,
1983.
Statistical
pocket
book
of
Bangladesh.
Bangladesh
Bureau
of
Statistics, Statistics Division, Ministry of Planning, Dhaka. pag. var.
Berka, R. Freshwater fishpond management. In Ecosystems of the World. Elsevier
Science Publishers, Amsterdam (in press).
RS. V. Fall…
For
example,
in
the
tropics,
combining a
benthic
feeder
(common carp), the
vegetation consumption/Eaecal fertilization
effects of grass carp,
a
good general
'mopping
up‘
species
(like rohu)
and
opportunistic
microphagous species
(like
tilapias) would provide a
mixture of versatile species, all of which could
respond
to
various intensities of supplemental feeding and the com binations of which c0uld
be
varied according to
demand and
value.
Other
species, e.g. catla,
eculd be
added according to demand.
The interrelationships
of
auto—
and
heterotrophic
food webs
in wastefed
systems
also merit further study.
The technique
of tracing food webs by carbon
isotopes (Schroeder, 1983) is an important tool. In the tropics, there seems to be a
limit to fertilized
pond
production without supplementatal feeding
and
aeration,
allowing
higher
stocking.
Where these are
unaffordable,
greater yields
could
perhaps be obtained by better
manipulation and
enhancement
of planktonic
and
detrital food sources.
E — Diseases
Carps suffer from
many diseases, especially
when under stress from adverse
environments and poor nutrition.
Many carp microbial pathogens and parasites are
ubiquitous (e.g.., trichodinid protozoans and ectoparasitic crustaceans). Some have
been spread with fish transfers, e.g. lchthvophthirius,
Lernaea
and
Myxobolus to
Indonesia.
Disease problems are generally more serious at low temperatures and in
temperate
regions
than
in the
tropics,
apart
from
the
periodic
devastating
outbreaks of ulcerative diseases recorded in Southeast Asia
(Aeromonas spp. have
been cited as
primary pathogens,
but many secondary invaders —
bacteria, fungi
and protozoa — are
involved).
Recent trends include a stronger awareness of the
need
for stricter quarantine
procedures (IDRC, 1983),
and increasing interest
by
major
drug companies to
develop
and supply compounds
for
hatchery
hygiene,
disease prophylaxie and
chemotherapy.
Despite this and the possible development
of
vaccines
and genetic resistance
to
diseases, good husbandry, good
nutrition,
high
standards of hygiene (especially in
hateheries) remain the
cultu1‘ist's
chief
safeguard.
ACKNOWLEGEMENTS
I wish to thank all those who helped with information for the compilation of
this
review, especially, J.
Balarin,
R.
Berka,
T.
Bhukasawan, R. Billard, R.
Chilvers,
C.H. Fernando, H.F. Henderson, L. Horvath, K.H.
Ibrahim, M.R. Jaffa,
I—B. Kim, C.
Lee, Li Sifa, M.
von
Lukowicz, R.C. May, D. Mires, K. Pinter, J.
Stoneman and
W. Steffens.
REFERENCES
BBS.,
1983.
Statistical
book
of
Bangladesh.
Bangladesh
Bureau
of
Statistics, Statistics Division, Ministry of Planning, Dhaka. pag. var.
Berka, R. Freshwater fishpond management. In Ecosystems of the World. Elsevier
Science Publishers, Amsterdam (in press).