240
WILLIAM MACNAE
such strains arc useful for culture in freshwater or brackish water fish
ponds. Spread of tilapia into adjoining rice paddies is unpopular, the
males, in digging their nests, uproot too much of the young rice. Hence,
in spite of many advantages, tilapia is not Fopular, and attempts have
been made to exterminate it in many countries. ,
Occasionally, a t the beginning of the north-east monsoon, the pond
may be drained to be filled again a few weeks later. Fry are admitted
and adult chanos harvested twice a year. When the pond is drained
any other fish will be harvested and marketed.
There are many by-products, the most important being successive
crops of penaeid prawns. Seasonal swarms of mysids and small
sergestid prawns, Acetes spp., are caught, dried and made into a paste
used as a savoury. The prawn crop is a most useful adjunct and while
extreme yields of 740 kg per hectare (830 Ib per acre) have been
obtained yields of between 23 and 63 kg per hectare (25 and 70 Ib per
acre) are more usual.
I n the vicinity of large Chinese settlements elsewhere in South East
Asia, the ponds are used for the cultivation of prawns alone. The
techniques involved have been discussed at length by Hall (1962). A
pond is cut off from an inlet or bay in the mangal. To effect this a bund
is built up from materials locally available and a sluice or several
sluices are built into the bund. Prawn larvae are admitted by controlling the inflow of sea water and adults are caught by trapping them
in nets at the sluices on the outgoing tide at night. Many penaeids bury
themselves in the mud by day and swim around a t night. At periods
with suitable tides it may be possible to release water from the pond
twice on a single night. Fishing may take place on about twenty
nights per month. The yields are comparable with those of the ponds
in Java.
The large mangrove crab, Scylla serrata, also occurs abundantly in
the tambaks of Java and the prawn ponds. It is not popular with the
caretakers of the ponds for its burrows may run through the bunds and
endanger their structure. None the less they are a popular article of
diet with those who can obtain them. Many snails, species of Cerithidea
and Telescopium telescopium, abound on the bottom of the ponds
These too are collected and eaten.
subsisting on the semi-fluid humus layer that so often collects
C. Reclamation
Many of the low lying coconut groves in Ceylon and in the vicinity
of Quelimane iii central Moqambique, just north of the Zambezi delta,
are reclaimed mangals. The trees were felled, the slash piled into rows,
WILLIAM MACNAE
such strains arc useful for culture in freshwater or brackish water fish
ponds. Spread of tilapia into adjoining rice paddies is unpopular, the
males, in digging their nests, uproot too much of the young rice. Hence,
in spite of many advantages, tilapia is not Fopular, and attempts have
been made to exterminate it in many countries. ,
Occasionally, a t the beginning of the north-east monsoon, the pond
may be drained to be filled again a few weeks later. Fry are admitted
and adult chanos harvested twice a year. When the pond is drained
any other fish will be harvested and marketed.
There are many by-products, the most important being successive
crops of penaeid prawns. Seasonal swarms of mysids and small
sergestid prawns, Acetes spp., are caught, dried and made into a paste
used as a savoury. The prawn crop is a most useful adjunct and while
extreme yields of 740 kg per hectare (830 Ib per acre) have been
obtained yields of between 23 and 63 kg per hectare (25 and 70 Ib per
acre) are more usual.
I n the vicinity of large Chinese settlements elsewhere in South East
Asia, the ponds are used for the cultivation of prawns alone. The
techniques involved have been discussed at length by Hall (1962). A
pond is cut off from an inlet or bay in the mangal. To effect this a bund
is built up from materials locally available and a sluice or several
sluices are built into the bund. Prawn larvae are admitted by controlling the inflow of sea water and adults are caught by trapping them
in nets at the sluices on the outgoing tide at night. Many penaeids bury
themselves in the mud by day and swim around a t night. At periods
with suitable tides it may be possible to release water from the pond
twice on a single night. Fishing may take place on about twenty
nights per month. The yields are comparable with those of the ponds
in Java.
The large mangrove crab, Scylla serrata, also occurs abundantly in
the tambaks of Java and the prawn ponds. It is not popular with the
caretakers of the ponds for its burrows may run through the bunds and
endanger their structure. None the less they are a popular article of
diet with those who can obtain them. Many snails, species of Cerithidea
and Telescopium telescopium, abound on the bottom of the ponds
These too are collected and eaten.
subsisting on the semi-fluid humus layer that so often collects
C. Reclamation
Many of the low lying coconut groves in Ceylon and in the vicinity
of Quelimane iii central Moqambique, just north of the Zambezi delta,
are reclaimed mangals. The trees were felled, the slash piled into rows,