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C. F. HICKLING
more of which may be used for fishing as well as for the exchange of
water.
Generally speaking, brackish-water fishponds are shallow, in
recognition of the fact that in estuaries the benthos is the chief primary
source of food and not the plankton ; therefore high and costly banks
are not usually needed except for the perimeter flood dyke. The banks
separating the brackish-water fishponds of Hong Kong are 8-10 ft high,
but this is to enable as much rain water as possible to be collected
during the season. These ponds are only very slightly brackish (Ti
Chow, 1958), and do not normally exceed 1.4 chlorinity per thousand.
They rely on rainfall, and this slight brackishness is due to salt in the
soil since the ponds are on land reclaimed from salt marsh.
The marine fishponds on the Biscay coast of France were put up
two centuries ago and there seem to have been no additions since. As
described by Arne (1938), the 300 hectares of ponds are surrounded by
a strong perimeter dyke, 6 m wide at the top and carrying a roadway;
the seaward slope of the bank is 11.5 m long and revetted with fascines.
The inner banks are grassy. A deep ditch around the inner side of the
banks is doubtless the original borrow pit, but is also the “ deep ”
where the fish may shelter in cold weather or too hot weather. Apart
from the “deep”, the pond is very shallow, only 40-50 cm, and Arne says
these shallow areas warm up quickly and grow the maximum amount
of useful food for the fish, which are chiefly grey mullet and eels.
The Russian limans, though often of very large size, are not subdivided by embankments into ponds.
Cobb (1901) writes that one of the largest of the original ponds on
Hawaii was built by the forced labour of the people of a local king,
who made them pass lava blocks from hand to hand to build the walls
of the pond. These ponds stand on coral reef flats, so excavation seems
unnecessary or impossible.
In the upper deltaic parts of great estuaries such as that of the
Pearl River in Kwangtung Province of China, there may still be a
large rise and fall of tide even though the water is wholly fresh. These
changes of level are used to operate huge fishpond systems which are of
great antiquity, and which, covering 60% of the surface of a large delta,
are probably the most extensive in the world. These ponds can be
completely emptied at low tide and refilled at high tide to a depth of
several feet. They are stocked with fresh-water fish, and may also be
used alternately as ricefields. As the techniques of fish culture are
those of intensive fresh-water fish farming, they will not be further
considered here. Similar regions at the head of the deltas of great
rivers such as the Niger might offer similar possibilities.
C. F. HICKLING
more of which may be used for fishing as well as for the exchange of
water.
Generally speaking, brackish-water fishponds are shallow, in
recognition of the fact that in estuaries the benthos is the chief primary
source of food and not the plankton ; therefore high and costly banks
are not usually needed except for the perimeter flood dyke. The banks
separating the brackish-water fishponds of Hong Kong are 8-10 ft high,
but this is to enable as much rain water as possible to be collected
during the season. These ponds are only very slightly brackish (Ti
Chow, 1958), and do not normally exceed 1.4 chlorinity per thousand.
They rely on rainfall, and this slight brackishness is due to salt in the
soil since the ponds are on land reclaimed from salt marsh.
The marine fishponds on the Biscay coast of France were put up
two centuries ago and there seem to have been no additions since. As
described by Arne (1938), the 300 hectares of ponds are surrounded by
a strong perimeter dyke, 6 m wide at the top and carrying a roadway;
the seaward slope of the bank is 11.5 m long and revetted with fascines.
The inner banks are grassy. A deep ditch around the inner side of the
banks is doubtless the original borrow pit, but is also the “ deep ”
where the fish may shelter in cold weather or too hot weather. Apart
from the “deep”, the pond is very shallow, only 40-50 cm, and Arne says
these shallow areas warm up quickly and grow the maximum amount
of useful food for the fish, which are chiefly grey mullet and eels.
The Russian limans, though often of very large size, are not subdivided by embankments into ponds.
Cobb (1901) writes that one of the largest of the original ponds on
Hawaii was built by the forced labour of the people of a local king,
who made them pass lava blocks from hand to hand to build the walls
of the pond. These ponds stand on coral reef flats, so excavation seems
unnecessary or impossible.
In the upper deltaic parts of great estuaries such as that of the
Pearl River in Kwangtung Province of China, there may still be a
large rise and fall of tide even though the water is wholly fresh. These
changes of level are used to operate huge fishpond systems which are of
great antiquity, and which, covering 60% of the surface of a large delta,
are probably the most extensive in the world. These ponds can be
completely emptied at low tide and refilled at high tide to a depth of
several feet. They are stocked with fresh-water fish, and may also be
used alternately as ricefields. As the techniques of fish culture are
those of intensive fresh-water fish farming, they will not be further
considered here. Similar regions at the head of the deltas of great
rivers such as the Niger might offer similar possibilities.