ESTUARINE FISH FARMING
131
dyke, the dykes dividing the enclosed area can be very low, since they
donot have to face large waves (Figs. 3 and 10). The small waves
which are encountered are rendered harmless to the dykes by pegging
rice straw on the leeward banks (Fig. 3). The level of water in the
distributory canals, and therefore in the ponds, is controlled by sluices
in the main storm dyke. Because the dykes are low, the productive
area of the ponds is a high proportion of the area enclosed by the
storm dyke.
Lin sketches an ideal layout (Fig. 5 ) , showing that 94% of a pond
area of 20 hectares could be allotted to productive ponds, and only 6%
to canals, nursery and wintering ponds, passageways and refuges.
The sluices in the storm dyke are substantial structures made of
concrete or brick, and are important items in capital costs, but the
sluices between the ponds can be cheap wooden slats sliding in grooves
in small concrete or brick posts (Fig. 10).
I n the Philippines, earth-moving machinery can be used in making
the 3 000 hectares of new fishponds which are annually added to the
country’s resources. I n Java, according to Schuster (1952), hand
labour has been used for pond construction but this will have to be
changed, since “ the costs of local labour do not permit profitable
execution of such activities in the old-fashioned way ”. Mobile teams
equipped with modern machinery will have t o carry out the work, and
Schuster thinks that, in spite of many difficulties, the importance of
this kind of work is too great to be indefinitely postponed.
I n Java, the construction of a brackish-water fishpond begins
with the excavation by hand of a ditch 3-5 yd wide to encircle the
periphery of the future pond. The excavated soil is thrown on the outside so as to form a protective dyke (Fig. 4). At this stage, sluices are
placed in position in gaps in the dyke; their dimensions may vary,
and costs depend on whether they are made of wood, brick or, concrete.
Moreover, in a soft soil, heavy sluices would have to be supported on
piles, and though local mangrove wood could be used, this would be
an additional cost. The soil moving may be done on contract by itinerant gangs of specialist workmen, but Schuster says that it is usual
for the completion of a pond system to be extended over many
years, as money becomes available to be ploughed back into the
business. From a sample survey, Schuster estimated that only about
5 % of the total vast area of ponds on Java could be regarded as finally
completed. No less than 8.7% was occupied by embankments, and
21% was “ high ground ” (that is, incompletely excavated so that it
was not covered by water). Thus, Schuster estimated that the nominal
area of some 200 000 acres occupied by the fishponds represented
131
dyke, the dykes dividing the enclosed area can be very low, since they
donot have to face large waves (Figs. 3 and 10). The small waves
which are encountered are rendered harmless to the dykes by pegging
rice straw on the leeward banks (Fig. 3). The level of water in the
distributory canals, and therefore in the ponds, is controlled by sluices
in the main storm dyke. Because the dykes are low, the productive
area of the ponds is a high proportion of the area enclosed by the
storm dyke.
Lin sketches an ideal layout (Fig. 5 ) , showing that 94% of a pond
area of 20 hectares could be allotted to productive ponds, and only 6%
to canals, nursery and wintering ponds, passageways and refuges.
The sluices in the storm dyke are substantial structures made of
concrete or brick, and are important items in capital costs, but the
sluices between the ponds can be cheap wooden slats sliding in grooves
in small concrete or brick posts (Fig. 10).
I n the Philippines, earth-moving machinery can be used in making
the 3 000 hectares of new fishponds which are annually added to the
country’s resources. I n Java, according to Schuster (1952), hand
labour has been used for pond construction but this will have to be
changed, since “ the costs of local labour do not permit profitable
execution of such activities in the old-fashioned way ”. Mobile teams
equipped with modern machinery will have t o carry out the work, and
Schuster thinks that, in spite of many difficulties, the importance of
this kind of work is too great to be indefinitely postponed.
I n Java, the construction of a brackish-water fishpond begins
with the excavation by hand of a ditch 3-5 yd wide to encircle the
periphery of the future pond. The excavated soil is thrown on the outside so as to form a protective dyke (Fig. 4). At this stage, sluices are
placed in position in gaps in the dyke; their dimensions may vary,
and costs depend on whether they are made of wood, brick or, concrete.
Moreover, in a soft soil, heavy sluices would have to be supported on
piles, and though local mangrove wood could be used, this would be
an additional cost. The soil moving may be done on contract by itinerant gangs of specialist workmen, but Schuster says that it is usual
for the completion of a pond system to be extended over many
years, as money becomes available to be ploughed back into the
business. From a sample survey, Schuster estimated that only about
5 % of the total vast area of ponds on Java could be regarded as finally
completed. No less than 8.7% was occupied by embankments, and
21% was “ high ground ” (that is, incompletely excavated so that it
was not covered by water). Thus, Schuster estimated that the nominal
area of some 200 000 acres occupied by the fishponds represented